Almost Blank Subframe Allocation in Heterogeneous Network

ABSTRACT

A first base station provides overlapping coverage area with second base stations and third base stations. Second base stations allow access to wireless devices and configure a second plurality of almost blank subframes. Second base stations configure the same set of subframes as the second plurality of almost blank subframes. Third base stations allow access to a restricted subset of wireless devices and configure a third plurality of almost blank subframes. At least two base stations in the third base stations configure different set of subframes as the second plurality of almost blank subframes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 14/574,686,filed Dec. 18, 2014, which is a continuation of application Ser. No.13/662,503, filed Oct. 28, 2012, which claims the benefit of U.S.Provisional Application No. 61/553,184, filed Oct. 29, 2011, and U.S.Provisional Application No. 61/553,186, filed Oct. 29, 2011, which arehereby incorporated by reference in its entirety.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Examples of several of the various embodiments of the present inventionare described herein with reference to the drawings, in which:

FIG. 1 is a diagram depicting example sets of OFDM subcarriers as per anaspect of an embodiment of the present invention;

FIG. 2 is a diagram depicting an example transmission time and receptiontime for two carriers as per an aspect of an embodiment of the presentinvention;

FIG. 3 is a diagram depicting OFDM radio resources as per an aspect ofan embodiment of the present invention;

FIG. 4 is a block diagram of a base station and a wireless device as peran aspect of an embodiment of the present invention;

FIG. 5 is a block diagram depicting a system for transmitting datatraffic over an OFDM radio system as per an aspect of an embodiment ofthe present invention;

FIG. 6 is a diagram depicting an example heterogeneous network as per anaspect of an embodiment of the present invention;

FIG. 7 is a diagram illustrating a few example interference scenarios asper an aspect of an embodiment of the present invention;

FIG. 8 is a diagram depicting an example almost blank subframe as per anaspect of an embodiment of the present invention;

FIG. 9 is an example almost blank subframe configuration as per anaspect of an embodiment of the present invention; and

FIG. 10 is a diagram depicting an example wireless device configurationas per an aspect of an embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Example embodiments of the present invention enable special subframeallocation in wireless communication systems. Embodiments of thetechnology disclosed herein may be employed, for example, in thetechnical field of heterogeneous wireless communication systems. Moreparticularly, the embodiments of the technology disclosed herein mayrelate to providing dynamic special subframe allocation in heterogeneouswireless communication systems.

Example embodiments of the invention may be implemented using variousphysical layer modulation and transmission mechanisms. Exampletransmission mechanisms may include, but are not limited to: CDMA (codedivision multiple access), OFDM (orthogonal frequency divisionmultiplexing), TDMA (time division multiple access), Wavelettechnologies, and/or the like. Hybrid transmission mechanisms such asTDMA/CDMA, and OFDM/CDMA may also be employed. Various modulationschemes may be applied for signal transmission in the physical layer.Examples of modulation schemes include, but are not limited to: phase,amplitude, code, a combination of these, and/or the like. An exampleradio transmission method may implement QAM (quadrature amplitudemodulation) using BPSK (binary phase shift keying), QPSK (quadraturephase shift keying), 16-QAM, 64-QAM, 256-QAM, and/or the like. Physicalradio transmission may be enhanced by dynamically or semi-dynamicallychanging the modulation and coding scheme depending on transmissionrequirements and radio conditions.

FIG. 1 is a diagram depicting example sets of OFDM subcarriers as per anaspect of an embodiment of the present invention. As illustrated in thisexample, arrow(s) in the diagram may depict a subcarrier in amulticarrier OFDM system. The OFDM system may use technology such asOFDM technology, SC-OFDM (single carrier-OFDM) technology, or the like.For example, arrow 101 shows a subcarrier transmitting informationsymbols. FIG. 1 is for illustration purposes, and a typical multicarrierOFDM system may include more subcarriers in a carrier. For example, thenumber of subcarriers in a carrier may be in the range of 10 to 10,000subcarriers. FIG. 1 shows two guard bands 106 and 107 in a transmissionband. As illustrated in FIG. 1, guard band 106 is between subcarriers103 and subcarriers 104. The example set of subcarriers A 102 includessubcarriers 103 and subcarriers 104. FIG. 1 also illustrates an exampleset of subcarriers B 105. As illustrated, there is no guard band betweenany two subcarriers in the example set of subcarriers B 105. Carriers ina multicarrier OFDM communication system may be contiguous carriers,non-contiguous carriers, or a combination of both contiguous andnon-contiguous carriers.

FIG. 2 is a diagram depicting an example transmission time and receptiontime for two carriers as per an aspect of an embodiment of the presentinvention. A multicarrier OFDM communication system may include one ormore carriers, for example, ranging from 1 to 10 carriers. Carrier A 204and carrier B 205 may have the same or different timing structures.Although FIG. 2 shows two synchronized carriers, carrier A 204 andcarrier B 205 may or may not be synchronized with each other. Differentradio frame structures may be supported for FDD (frequency divisionduplex) and TDD (time division duplex) duplex mechanisms. FIG. 2 showsan example FDD frame timing. Downlink and uplink transmissions may beorganized into radio frames 201. In this example, radio frame durationis 10 msec. Other frame durations, for example, in the range of 1 to 100msec may also be supported. In this example, each 10 ms radio frame 201may be divided into ten equally sized sub-frames 202. Other subframedurations such as including 0.5 msec, 1 msec, 2 msec, and 5 msec mayalso be supported. Sub-frame(s) may consist of two or more slots 206.For the example of FDD, 10 subframes may be available for downlinktransmission and 10 subframes may be available for uplink transmissionsin each 10 ms interval. Uplink and downlink transmissions may beseparated in the frequency domain. Slot(s) may include a plurality ofOFDM symbols 203. The number of OFDM symbols 203 in a slot 206 maydepend on the cyclic prefix length and subcarrier spacing.

In an example case of TDD, uplink and downlink transmissions may beseparated in the time domain. According to some of the various aspectsof embodiments, each 10 ms radio frame may include two half-frames of 5ms each. Half-frame(s) may include eight slots of length 0.5 ms andthree special fields: DwPTS (Downlink Pilot Time Slot), GP (GuardPeriod) and UpPTS (Uplink Pilot Time Slot). The length of DwPTS andUpPTS may be configurable subject to the total length of DwPTS, GP andUpPTS being equal to 1 ms. Both 5 ms and 10 ms switch-point periodicitymay be supported. In an example, subframe 1 in all configurations andsubframe 6 in configurations with 5 ms switch-point periodicity mayinclude DwPTS, GP and UpPTS. Subframe 6 in configurations with 10 msswitch-point periodicity may include DwPTS. Other subframes may includetwo equally sized slots. For this TDD example, GP may be employed fordownlink to uplink transition. Other subframes/fields may be assignedfor either downlink or uplink transmission. Other frame structures inaddition to the above two frame structures may also be supported, forexample in one example embodiment the frame duration may be selecteddynamically based on the packet sizes.

FIG. 3 is a diagram depicting OFDM radio resources as per an aspect ofan embodiment of the present invention. The resource grid structure intime 304 and frequency 305 is illustrated in FIG. 3. The quantity ofdownlink subcarriers or resource blocks (RB) (in this example 6 to 100RBs) may depend, at least in part, on the downlink transmissionbandwidth 306 configured in the cell. The smallest radio resource unitmay be called a resource element (e.g. 301). Resource elements may begrouped into resource blocks (e.g. 302). Resource blocks may be groupedinto larger radio resources called Resource Block Groups (RBG) (e.g.303). The transmitted signal in slot 206 may be described by one orseveral resource grids of a plurality of subcarriers and a plurality ofOFDM symbols. Resource blocks may be used to describe the mapping ofcertain physical channels to resource elements. Other pre-definedgroupings of physical resource elements may be implemented in the systemdepending on the radio technology. For example, 24 subcarriers may begrouped as a radio block for a duration of 5 msec.

Physical and virtual resource blocks may be defined. A physical resourceblock may be defined as N consecutive OFDM symbols in the time domainand M consecutive subcarriers in the frequency domain, wherein M and Nare integers. A physical resource block may include M×N resourceelements. In an illustrative example, a resource block may correspond toone slot in the time domain and 180 kHz in the frequency domain (for 15KHz subcarrier bandwidth and 12 subcarriers). A virtual resource blockmay be of the same size as a physical resource block. Various types ofvirtual resource blocks may be defined (e.g. virtual resource blocks oflocalized type and virtual resource blocks of distributed type). Forvarious types of virtual resource blocks, a pair of virtual resourceblocks over two slots in a subframe may be assigned together by a singlevirtual resource block number. Virtual resource blocks of localized typemay be mapped directly to physical resource blocks such that sequentialvirtual resource block k corresponds to physical resource block k.Alternatively, virtual resource blocks of distributed type may be mappedto physical resource blocks according to a predefined table or apredefined formula. Various configurations for radio resources may besupported under an OFDM framework, for example, a resource block may bedefined as including the subcarriers in the entire band for an allocatedtime duration.

According to some of the various aspects of embodiments, an antenna portmay be defined such that the channel over which a symbol on the antennaport is conveyed may be inferred from the channel over which anothersymbol on the same antenna port is conveyed. In some embodiments, theremay be one resource grid per antenna port. The set of antenna port(s)supported may depend on the reference signal configuration in the cell.Cell-specific reference signals may support a configuration of one, two,or four antenna port(s) and may be transmitted on antenna port(s) {0},{0, 1}, and {0, 1, 2, 3}, respectively. Multicast-broadcast referencesignals may be transmitted on antenna port 4. Wireless device-specificreference signals may be transmitted on antenna port(s) 5, 7, 8, or oneor several of ports {7, 8, 9, 10, 11, 12, 13, 14}. Positioning referencesignals may be transmitted on antenna port 6. Channel state information(CSI) reference signals may support a configuration of one, two, four oreight antenna port(s) and may be transmitted on antenna port(s) 15, {15,16}, {15, . . . ,18} and {15, . . . ,22}, respectively. Variousconfigurations for antenna configuration may be supported depending onthe number of antennas and the capability of the wireless devices andwireless base stations.

According to some embodiments, a radio resource framework using OFDMtechnology may be employed. Alternative embodiments may be implementedemploying other radio technologies. Example transmission mechanismsinclude, but are not limited to: CDMA, OFDM, TDMA, Wavelet technologies,and/or the like. Hybrid transmission mechanisms such as TDMA/CDMA, andOFDM/CDMA may also be employed.

FIG. 4 is an example block diagram of a base station 401 and a wirelessdevice 406, as per an aspect of an embodiment of the present invention.A communication network 400 may include at least one base station 401and at least one wireless device 406. The base station 401 may includeat least one communication interface 402, at least one processor 403,and at least one set of program code instructions 405 stored innon-transitory memory 404 and executable by the at least one processor403. The wireless device 406 may include at least one communicationinterface 407, at least one processor 408, and at least one set ofprogram code instructions 410 stored in non-transitory memory 409 andexecutable by the at least one processor 408. Communication interface402 in base station 401 may be configured to engage in communicationwith communication interface 407 in wireless device 406 via acommunication path that includes at least one wireless link 411.Wireless link 411 may be a bi-directional link. Communication interface407 in wireless device 406 may also be configured to engage in acommunication with communication interface 402 in base station 401. Basestation 401 and wireless device 406 may be configured to send andreceive data over wireless link 411 using multiple frequency carriers.According to some of the various aspects of embodiments, transceiver(s)may be employed. A transceiver is a device that includes both atransmitter and receiver. Transceivers may be employed in devices suchas wireless devices, base stations, relay nodes, and/or the like.Example embodiments for radio technology implemented in communicationinterface 402, 407 and wireless link 411 are illustrated are FIG. 1,FIG. 2, and FIG. 3. and associated text.

FIG. 5 is a block diagram depicting a system 500 for transmitting datatraffic generated by a wireless device 502 to a server 508 over amulticarrier OFDM radio according to one aspect of the illustrativeembodiments. The system 500 may include a Wireless CellularNetwork/Internet Network 507, which may function to provide connectivitybetween one or more wireless devices 502 (e.g., a cell phone, PDA(personal digital assistant), other wirelessly-equipped device, and/orthe like), one or more servers 508 (e.g. multimedia server, applicationservers, email servers, or database servers) and/or the like.

It should be understood, however, that this and other arrangementsdescribed herein are set forth for purposes of example only. As such,those skilled in the art will appreciate that other arrangements andother elements (e.g., machines, interfaces, functions, orders offunctions, etc.) may be used instead, some elements may be added, andsome elements may be omitted altogether. Further, as in mosttelecommunications applications, those skilled in the art willappreciate that many of the elements described herein are functionalentities that may be implemented as discrete or distributed componentsor in conjunction with other components, and in any suitable combinationand location. Still further, various functions described herein as beingperformed by one or more entities may be carried out by hardware,firmware and/or software logic in combination with hardware. Forinstance, various functions may be carried out by a processor executinga set of machine language instructions stored in memory.

As shown, the access network may include a plurality of base stations503 . . . 504. Base station 503 . . . 504 of the access network mayfunction to transmit and receive RF (radio frequency) radiation 505 . .. 506 at one or more carrier frequencies, and the RF radiation mayprovide one or more air interfaces over which the wireless device 502may communicate with the base stations 503 . . . 504. The user 501 mayuse the wireless device (or UE: user equipment) to receive data traffic,such as one or more multimedia files, data files, pictures, video files,or voice mails, etc. The wireless device 502 may include applicationssuch as web email, email applications, upload and ftp applications, MMS(multimedia messaging system) applications, or file sharingapplications. In another example embodiment, the wireless device 502 mayautomatically send traffic to a server 508 without direct involvement ofa user. For example, consider a wireless camera with automatic uploadfeature, or a video camera uploading videos to the remote server 508, ora personal computer equipped with an application transmitting traffic toa remote server.

One or more base stations 503 . . . 504 may define a correspondingwireless coverage area. The RF radiation 505 . . . 506 of the basestations 503 . . . 504 may carry communications between the WirelessCellular Network/Internet Network 507 and access device 502 according toany of a variety of protocols. For example, RF radiation 505 . . . 506may carry communications according to WiMAX (Worldwide Interoperabilityfor Microwave Access e.g., IEEE 802.16), LTE (long term evolution),microwave, satellite, MMDS (Multichannel Multipoint DistributionService), Wi-Fi (e.g., IEEE 802.11), Bluetooth, infrared, and otherprotocols now known or later developed. The communication between thewireless device 502 and the server 508 may be enabled by any networkingand transport technology for example TCP/IP (transport controlprotocol/Internet protocol), RTP (real time protocol), RTCP (real timecontrol protocol), HTTP (Hypertext Transfer Protocol) or any othernetworking protocol.

According to some of the various aspects of embodiments, an LTE networkmay include many base stations, providing a user plane (PDCP: packetdata convergence protocol/RLC: radio link control/MAC: media accesscontrol/PHY: physical) and control plane (RRC: radio resource control)protocol terminations towards the wireless device. The base station(s)may be interconnected with other base station(s) by means of an X2interface. The base stations may also be connected by means of an S1interface to an EPC (Evolved Packet Core). For example, the basestations may be interconnected to the MME (Mobility Management Entity)by means of the S1-MME interface and to the Serving Gateway (S-GW) bymeans of the S1-U interface. The S1 interface may support a many-to-manyrelation between MMEs/Serving Gateways and base stations. A base stationmay include many sectors for example: 1, 2, 3, 4, or 6 sectors. A basestation may include many cells, for example, ranging from 1 to 50 cellsor more. A cell may be categorized, for example, as a primary cell orsecondary cell. When carrier aggregation is configured, a wirelessdevice may have one RRC connection with the network. At RRC connectionestablishment/re-establishment/handover, one serving cell may providethe NAS (non-access stratum) mobility information (e.g. TAI-trackingarea identifier), and at RRC connection re-establishment/handover, oneserving cell may provide the security input. This cell may be referredto as the Primary Cell (PCell). In the downlink, the carriercorresponding to the PCell may be the Downlink Primary Component Carrier(DL PCC), while in the uplink, it may be the Uplink Primary ComponentCarrier (UL PCC). Depending on wireless device capabilities, SecondaryCells (SCells) may be configured to form together with the PCell a setof serving cells. In the downlink, the carrier corresponding to an SCellmay be a Downlink Secondary Component Carrier (DL SCC), while in theuplink, it may be an Uplink Secondary Component Carrier (UL SCC). AnSCell may or may not have an uplink carrier.

A cell, comprising a downlink carrier and optionally an uplink carrier,is assigned a physical cell ID and a cell index. A carrier (downlink oruplink) belongs to only one cell, the cell ID or Cell index may alsoidentify the downlink carrier or uplink carrier of the cell (dependingon the context it is used). In the specification, cell ID may be equallyreferred to a carrier ID, and cell index may be referred to carrierindex. In implementation, the physical cell ID or cell index may beassigned to a cell. Cell ID may be determined using the synchronizationsignal transmitted on a downlink carrier. Cell index may be determinedusing RRC messages. For example, when the specification refers to afirst physical cell ID for a first downlink carrier, it may mean thefirst physical cell ID is for a cell comprising the first downlinkcarrier. The same concept may apply to, for example, carrier activation.When the specification indicates that a first carrier is activated, itequally means that the cell comprising the first carrier is activated.

Embodiments may be configured to operate as needed. The disclosedmechanism may be performed when certain criteria are met, for example,in wireless device, base station, radio environment, network, acombination of the above, and/or the like. Example criteria may bebased, at least in part, on for example, traffic load, initial systemset up, packet sizes, traffic characteristics, a combination of theabove, and/or the like. When the one or more criteria are met, theexample embodiments may be applied. Therefore, it may be possible toimplement example embodiments that selectively implement disclosedprotocols.

FIG. 6 shows an example heterogeneous network in an example embodiment.The coverage and capacity of macro base station 601 may be extended bythe utilization of base stations with lower transmit power. Micro, Pico,femto and relay nodes are examples of low power base stations. In anexample embodiment, pico base stations (or pico-cell) 602, 603, and 607may have transmit power ranges from approximately 200 mW toapproximately 5 W. Macro base stations may have a transmit power thattypically varies between 5 and 100 W. Femto base stations (orfemto-cells) may be used for local services such as in indoor services,and their transmit power may be approximately 200 mW or less. These arejust some example power ranges, and as such, should not be considered asa hard limit on the transmit power of a base station type. For example,some femto-cell product may transmit at a power greater than 200 mW.Femto or pico base stations 605, 606 may be configured with a restrictedsubscriber group that may allow access only to its closed subscribergroup (CSG) members. Such femto or pico base stations may be referred toas closed femtos or picos. Femto or pico base stations may also beconfigured as open femtos 604 or picos 602, 603. Relay Nodes (e.g. 608)may employ the macro base stations air interface as a backhaul and mayincrease coverage and capacity of the macro base station. A network thatcomprises of a mix of macro base stations and low-power nodes such aspico or femto base stations, where some base stations may be configuredwith restricted access and some may lack a wired backhaul, is referredto as a heterogeneous network.

Femto cells may be classified as open or closed depending on whether thefemto cells allow access to all, or to a restricted set of wirelessdevices. Closed femtos may restrict the access to a closed subscribergroup (CSG). Open femtos may be similar to pico-cells, but may use thenetwork backhaul provided by the home network. A femto cell may also bea hybrid, whereby many wireless devices may have access, but with lowerpriority for the wireless devices that do not belong to the femto'ssubscriber group. Closed femtos may not allow access to wirelessdevices, and may become a source of interference to those wirelessdevices. Co-channel deployments of closed femtos may cause coverageholes and hence outage of a size proportional to the transmit power ofthe femto-cell. Femto-cells may or may not have an X2 interface.OAM-based or X2 based techniques in conjunction with possibly autonomouspower control techniques may be used for interference management withfemto cells depending on the existence of a femto X2 interface. Thesetechniques may reduce the outage and/or interference that these networknodes cause around them and enable reception of the signal from themacro-cell in close proximity to the closed femto.

Co-channel deployment of low-power nodes and high power nodes mayintroduce new challenges. The introduction of low-power nodes in a macronetwork may create an imbalance between uplink and downlink coverage.Due to the larger transmit power of the macro base station, the handoverboundary may be shifted closer to the low-power node. This shift maylead to severe uplink interference problems as wireless devices servedby macro base stations create strong interference to the low-powernodes. Given the relatively small footprint of low-power nodes,low-power nodes may become underutilized due to geographic changes indata traffic demand. The limited coverage of low-power nodes may be areason for limited performance gain in heterogeneous networks. Some ofthe deployed femto cells may have enforced restricted associations,which may create a coverage hole and may exacerbate the interferenceproblem.

FIG. 7 illustrates a few example interference scenarios in an exampleembodiment. The solid arrow shows the desired signal, and the arrow withthe dashed line shows the unwanted interference. Wireless device 701 maynot be a member of CSG cell 705 and may be roaming in the coverage areaof femto-cell 705. It may receive the signal from macro base station708, and may receive high interference from CSG pico-cell 705. Inanother example, wireless device 702 may not be a member of CSG cell 706and may be roaming in the coverage area of femto-cell 706. The wirelessdevice 702 may transmit a signal to base station 708 in the macro basestation uplink channel. The wireless device 702 may create highinterference for femto-cell 706. The wireless device 703 may not be amember of CSG cell 707 and may be roaming in the coverage area offemto-cell 707. The wireless device 703 may be a member of CSGfemto-cell 706 and may a transmit signal to femto-cell 706. The wirelessdevice 703 may create high interference for femto-cell 707. In anotherexample scenario, the wireless device 704 may be in the cell coverageedge of pico-cell 709. The wireless device 704 may receive a signal frompico-cell 709. The wireless device 704 may also receive highinterference from macro base station 708. As shown in these examples, inorder to cope with the interference, it may be required to introducetechniques that may adequately address these issues.

A new physical layer design in LTE networks may allow for flexible timeand frequency resource partitioning. This added flexibility may enablemacro- and femto/picocells to assign different time-frequency resourceblocks within a carrier or different carriers (if available) to theirrespective wireless devices. This is one of the inter-cell interferencecoordination (ICIC) techniques and may be used on a downlink or anuplink to mitigate interference. With additional complexity, jointprocessing of serving and interfering base station signals may furtherimprove the performance of heterogeneous networks.

According to some of the various aspects of embodiments, cell rangeexpansion through handover biasing and resource partitioning amongdifferent node power classes may decrease interference. The biasingmechanism may allow for load balancing. Depending on the bias value, thenetwork may control the number of wireless devices associated with thelow-power nodes and therefore control traffic demand at those nodes.Resource partitioning, which may be adaptive, may allow configurationand adjustment of interference protected resources, enabling wirelessdevices in a cell's expanded area to receive data. Resource partitioningtechniques may mitigate uplink and downlink interference and allownon-CSG member wireless devices to receive service when in proximity ofclosed femto-base stations.

In a heterogeneous network, the network nodes may be deployed in thesame frequency layer. Deploying low-power nodes at the same frequencylayer as the (high-power) macro-cells may present interference problemsin the case of closed femtos. Also, for the case of open access nodes(open femtos, pico-cells, and RNs), the coverage of the low-power nodesmay be overshadowed by the transmissions of the high-power nodes.Interference coordination techniques may solve these problems. Areduction of closed femto interference to the macro layer and aperformance increase from the introduction of open access low-powernodes may be achieved by interference control techniques. To enableefficient support of co-channel deployment of heterogeneous networks, aninterference management scheme may adapt to different traffic loads anddifferent numbers of low-power nodes at various geographical areas.

According to some of the various aspects of embodiments, resourcepartitioning may be employed for interference management in co-channeldeployments. To reach its full potential, resource partitioning may bepaired with interference-cancellation-capable wireless devices. Similarapproaches may be applied to micro, pico, femto, and relay nodes. Eachnode may have its own caveats. For example, the X2 backhaul link betweenthe macro and relay base stations may be over an LTE air interface. Inanother example, closed femto cells may create their own interferencechallenges. Femto base stations may lack an X2 interface and employstatic or dynamic interference management methods using OAM-based orsimilar solutions.

According to some of the various aspects of embodiments, adaptiveinterference management in LTE may be enabled through X2 backhaulcoordination of resources used for scheduling data traffic. Thegranularity of the negotiated resource may be a subframe. One of thevarious motivations behind resource partitioning may be to controlinterference and/or enable cell range expansion through cell biasing. Ina typical case, cell range expansion may be enabled to improve systemcapacity, and a cell bias may be applied to low-power nodes. The biasvalue may refer to a threshold that triggers a handover between twocells. A positive bias may enable a wireless device to be handed over toa pico-cell when the difference in the signal strength from the macro-and pico-cells drop below a bias value. The high-power node (macro basestation) may inform the low-power node (pico base station) of whichresources may be utilized for scheduling macro wireless device and whichsubframes would remain unutilized (almost blank subframes). Low-powernodes may be made aware of the interference pattern from a high-powerbase station and may schedule a wireless device in the cell extendedareas on subframes protected from high-power interference. That is,subframes corresponding to almost blank subframes at the high-power basestation.

According to some of the various aspects of embodiments, the X2interface may enable direct base station to base station interface forinter-cell interference coordination (ICIC). Co-channel deployments ofheterogeneous networks may require coordination of almost blanksubframes. Almost blank subframes may reduce the interference created bythe transmitting node while providing full legacy support. On almostblank subframes, base station may not schedule unicast traffic while itmay transmit acquisition channels and common reference signal to providelegacy support. FIG. 8 shows an example almost blank subframe. In thisexample CRS (R0, R1, R2, R3 signals) are transmitted only in the controlregion and are not transmitted in the data region. The interfering basestation may still transmit PSS, SSS, PBCH, and RSs to support legacyterminals. Some interference still may exist. In this example, no datamay be transmitted in almost blank subframes or data may be transmittedat a substantially lower power in almost blank subframes.

Interference coordination using almost blank subframes may be performedby means of a bitmap. Each bit in the bitmap may be mapped to a singlesubframe. The size of the bitmap may be, for example, 40 bits, resultingin the interference pattern repeating itself after 40 ms. FIG. 9 showsan example almost blank subframe configuration in an example embodiment.In this example embodiment, no data may be scheduled in almost blanksubframes (ABS). In another embodiment, data may be scheduled in almostblank subframes at a substantially lower power. Subframes 901, 902, 903,and 904 may be configured as ABS in the macro base station. When a macrobase station transmits an almost blank subframe, data may not bescheduled in that subframe (or data may be transmitted at asubstantially lower power). This may increase the coverage of the femtoor pico base stations close to that macro base station. Subframes 905and 906 may be configured as ABS in the femto base station. When thefemto base station transmits an almost blank subframe, data may not bescheduled in that subframe (or data may be transmitted at asubstantially lower power). This may increase coverage allowed for themacro base station or the neighboring femto base stations. In theexample of FIG. 9, the almost blank subframe pattern may be repeatedevery 10 msec. This is just an example and various configurations may bepossible. The almost blank subframe configuration may be changeddynamically according to load and traffic, time of the day, or manyother parameters. In an example embodiment, based on the data trafficdemand, the pattern may change as often as every 40 ms. Thecommunication between nodes may be peer to peer. Or it may be in amaster-slave relationship. The node creating dominant interferenceconditions may control which resources may be used to serve wirelessdevices in the cell range extension area. In an example scenario, amacro base station may be a master, and a pico base station may be aslave since cell range expansion would most frequently be establishedfor pico base stations. The cell range expansion may be desirable for amacro base station as well. A use case for cell range expansion at themacro base station may be to reduce the number of handovers. In ascenario with a large number of high-mobility users, the number ofhandovers in the network may become a problem, for example when in thedeployment of pico base stations the cells become small. The sameresource partitioning schemes may then be utilized to allow highmobility macro wireless devices to remain attached to a macro-cell whiledeep inside coverage of a pico-cell. In this case, the pico base stationmay restrict scheduling data traffic on some resources, allowingcoverage for high-mobility macro wireless devices.

According to some of the various aspects of embodiments, subframeresource partitioning may create an interference pattern that mayrequire a new radio resource measurement paradigm. As dominantinterference may potentially vary from one subframe to the other, inorder to ensure radio resource management measurement accuracy, it maybe needed to restrict measurements to a desired set of subframes. In anexample embodiment, it may be desirable to define anchorinterference-protected resources that may be utilized for radio resourcemeasurement. The 40-bit bitmap may include indications of whichsubframes may have static protection from interference and therefore maybe suitable for measurements. The remaining resources may change moreoften.

According to some of the various aspects of embodiments, the servingbase station may inform a wireless device of the set of subframes towhich the wireless device measurement may be restricted. A set ofsubframes may be configured for radio link monitoring and to check ifthe current connection is reliable enough. The same or a different setof subframes may be introduced for radio resource management, forexample, a handover decision. An additional set of subframes may besignaled for the measurement for some neighboring base stations. Thisconfiguration may be relatively static and may not change rapidly.Another set of subframes may be configured in the wireless device forchannel state information reporting and link adaptation. Two sets ofsubframes may be signaled to a wireless device for two different channelstate information types. For example, one may be for almost blanksubframes, and the other may be for normal subframes. This configurationmay change dynamically depending on the network configuration.

FIG. 10 illustrates example channel state information bitmaps and anexample radio link management bitmap. Subframe 1001 (subframe 3) issemi-statically configured as ABS and therefore it is used for radiolink management in a wireless device in a victim base station. Subframes1002, 1003, and 1004 (subframes 1, 6, and 8) are dynamically configuredas ABS subframes. CSI bitmap 1 is used for a first channel stateinformation measurement and CSI bitmap 2 is used for a second channelstate information measurement. This is an example, and variousconfigurations and bitmap lengths, such as 40 bits or 70 bits, may alsobe supported. When there is no X2 interface, a static OAM-based orsimilar solution may be employed. The same principle of extendingcoverage of one cell into the area covered by the other may be achieved.In this case, it may be the macro-cell service that needs to be extendedinto an area covered by the closed femto-cell.

The resource partitioning may reduce interference from the data channel.Interference from the acquisition channels and CRS signal may remain,since these signals may be transmitted for backward compatibilityreasons. Subframe time shifting may be utilized in FDD systems to reducecollision of the acquisition channels between base stations of differentpower classes that require partitioning, but may not be employed in TDDsystems. Interference mitigation for the acquisition channels may beneeded for cell range expansion to enable the wireless device to detectand acquire a weak cell and then measure and feedback the measurementreport to the network, which may be needed for handover and cell rangeexpansion.

CRS interference mitigation may improve system performance. CRSinterference may degrade turbo code performance and the overallsignal-to-interference-plus-noise radio (SINR). Therefore, the potentialgains of cell range expansion may be reduced. Given that acquisitionchannels and CRS may be broadcast at high power targeting wirelessdevices at the cell edge, a robust wireless device solution is feasible.

One of the various rationales for the wireless device solution for theacquisition signals and CRS interference mitigation is that interferencemay be estimated and subtracted so that in the end it may not representsignificant interference. Acquisition channels may be transmitted at thesame location in cells, which means that the acquisition channelsinterference may comprise acquisition channels from neighboringinterfering cells. This structure may lend itself to a design of aninterference canceller. A wireless device receiver first may decode thestrongest signal, may perform channel gain estimation toward theinterfering cell, may cancel the interfering signal, and may continuethe procedure until acquisition channels of the serving cell areacquired.

A similar procedure may be performed to remove CRS interference. Thedifference may be that CRS tones may also interfere with data tonessince interference between CRS tones between high-power and low-powernodes may be reduced by CRS tone shifting. The procedure may be similar.If strong CRS interference is detected, and after the channel gaintoward the interfering cell is estimated, the CRS signal may becancelled. The procedure may be repeated until interfering signals aresubtracted.

RRC messages are used to configure wireless device configurationparameters related to almost blank configuration and measurements. Anexample RRC message configuration in an example embodiment is describedin the following paragraphs. A subframe pattern bitmap may indicate thetime domain measurement resource restriction pattern for primary orsecondary carrier measurements (RSRP, RSRQ and the radio linkmonitoring). The bitmap length may be, for example, 40 bits. Anothersubframe bitmap may configure neighbor measurement patterns. A neighbormeasurement bitmap along with the list of cells for which the neighbormeasurement bitmap is applied may be transmitted to the wireless device.If the list of cells is not included, the wireless device may apply timedomain measurement resource restrictions for neighbor cells. Time domainmeasurement resource restriction patterns may be applicable to neighborcell RSRP and RSRQ measurements on a carrier frequency indicated by RRC.In an example embodiment, two CSI subframe pattern configuration bitmapsmay be transmitted to the wireless device. Each bit map may be 40 bitslong. The CSI configuration may include a channel quality index, a rankindicator, a precoding matrix indicator, a combination thereof, or thelike.

A base station may broadcast an ABS subframe configuration employingMBSFN (multi-cast, broadcast, single frequency network) subframeconfiguration broadcast or unicast messages. An example broadcastmessage is an RRC system information block. MBSFN or ABS subframeconfigurations may include a radio frame allocation period, a radioframe allocation offset, a subframe allocation bitmap, any combinationof these parameters, or the like. A radio frame allocation period may be1, 2, 4, 8, 16 or 32 frames. A radio frame allocation offset may be anumber between 1 to 7 subframes. A subframe allocation bitmap may be forone frame or four frames. Radio frames that contain MBSFN/ABS subframesmay occur when equation (SFN mod radio Frame Allocation Period=radioFrame Allocation Offset) is satisfied. Values 1 and 2 may not beapplicable to radio frame allocation period when four Frames are used.

According to some of the various aspects of embodiments, a subframeallocation bitmap may define the subframes that are allocated for MBSFNwithin the radio frame allocation period defined by the radio frameallocation period and the radio frame allocation offset. A subframeallocation bitmap for one frame may be six bits long and for four framesmay be 24 bits long. In a bit-map indicating MBSFN/ABS subframeallocation in four consecutive radio frames, a “1” may denote that thecorresponding subframe is allocated for MBSFN/ABS. The bitmap may beinterpreted as follows: For FDD: Starting from the first radio frame andfrom the first/leftmost bit in the bitmap, the allocation may apply tosubframes #1, #2, #3, #6, #7, and #8 in the sequence of the fourradio-frames. For TDD: Starting from the first radio frame and from thefirst/leftmost bit in the bitmap, the allocation applies to subframes#3, #4, #7, #8, and #9 in the sequence of the four radio-frames. Thelast four bits may not be used. Uplink subframes may not be allocated.

Other example configurations may be implemented. For example, an MBSFNsubframe configuration may be used to introduce ABS subframes andsubframes used for scheduling release 10 or above wireless devices. Forexample, an MBSFN configuration may introduce subframe 1, 3, 6 and 8 asMBSFN subframes in a frame. Then MBSFN subframe 1 may be used forscheduling release 10 or above wireless devices, and MBSFN subframe 3,6, and 8 may be used as almost blank subframes. Therefore, as seen inthis example, MBSFN configuration may indicate other types of subframesin addition to almost blank subframes. In another configuration, a basestation may use one or many of MBSFN subframes for broadcasting ormulticasting services. In a typical scenario, in which MBSFN may beconfigured, for example, for four frames, with a period of 40 msec,various configurations for combining ABS, MBSFN, and release 10 or abovesubframes may be possible. In this specification, ABS subframes may becalled special subframes.

According to some of the various aspects of embodiments, specialsubframes may be configured for the primary carrier (cell) as well asone or more secondary carriers (cells). The configuration parameters forthe measurement parameters of the secondary carrier(s) may employ thebitmaps with the same length and format of the configuration parametersof the primary carrier. In an example embodiment, the configurationparameters of special subframes for one or more secondary carriers maybe the same as the configuration parameters for the special subframeconfiguration of the primary carrier.

According to some of the various aspects of embodiments, non-backwardcompatible carriers may be configured with special subframes. In anon-backward compatible carrier special subframe, no common referencesignal may be transmitted during the special subframe. Or, data andreference signals in a non-backward compatible carrier special subframemay be transmitted at a substantially lower power to ensure that nointerference (to other cells) is observed during the special subframe.

Example embodiments of the invention may enable special subframeallocation in wireless communication systems. Other example embodimentsmay comprise a non-transitory tangible computer readable mediacomprising instructions executable by one or more processors to causespecial subframe allocation in wireless communication systems. Yet otherexample embodiments may comprise an article of manufacture thatcomprises a non-transitory tangible computer readable machine-accessiblemedium having instructions encoded thereon for enabling programmablehardware to cause a device (e.g. wireless communicator, UE, basestation, etc.) to enable special subframes allocation. The device mayinclude processors, memory, interfaces, and/or the like. Other exampleembodiments may comprise communication networks comprising devices suchas base stations, wireless devices (or user equipment: UE), servers,switches, antennas, and/or the like.

A network may comprise a plurality of base stations. Transmission timemay be divided into a plurality of frames. Each frame in the pluralityof frames may further be divided into a plurality of subframes. A firstbase station may comprise a communication interface, a processor, and amemory storing instructions that, when executed, cause the first basestation to perform certain functions. According to some of the variousaspects of embodiments, the first base station may transmit a firstmessage to a plurality of wireless devices in connected mode. The firstmessage may comprise an initial subframe allocation bitmap indicating aninitial plurality of subframes. The initial plurality of subframes maycomprise an initial plurality of special subframes. After an increase inthe number of the plurality of wireless devices or after an increase inthe traffic load of the first base station by an amount greater than aload value, the first base station may transmit a second message. Thesecond message may comprise an updated subframe allocation bitmapindicating a second plurality of subframes. The second plurality ofsubframes may comprise an updated plurality of special subframes. Theupdated plurality of special subframes may comprise a smaller number ofspecial subframes than the initial plurality of special subframes.During the majority of symbols of a special subframe of a base station,no signal may be transmitted by the base station or signals may betransmitted with substantially lower power compared with transmit powerof signals transmitted during a subframe which is not assigned as aspecial subframe (non-special subframe). Non-special subframes may alsobe called regular subframes. Data and reference signals during a specialsubframe may be transmitted at a substantially lower power to ensurethat no interference (to other cells) is observed during the specialsubframe.

According to some of the various aspects of embodiments, the first basestation may transmit a first message to a plurality of wireless devicesin connected mode. The first message may comprise an initial subframeallocation bitmap indicating an initial plurality of subframes. Theinitial plurality of subframes may comprise an initial plurality ofspecial subframes. After a decrease in the number of the plurality ofwireless devices or after a decrease in the traffic load of the firstbase station by an amount greater than a load value, the first basestation may transmit a second message. The second message may comprisean updated subframe allocation bitmap indicating a second plurality ofsubframes. The second plurality of subframes may comprise an updatedplurality of special subframes. The updated plurality of specialsubframes may comprise a greater number of special subframes than theinitial plurality of special subframes. During the majority of symbolsof a special subframe of a base station, no signal may be transmitted bythe base station or signals may be transmitted with substantially lowerpower compared with transmit power of signals transmitted during asubframe which is not assigned as a special subframe.

According to some of the various aspects of embodiments, the first basestation may transmit a first message to a plurality of wireless devicesin connected mode. The first message may comprise at least one of thefollowing: a) an initial subframe allocation repetition period in termsof n frames, wherein n is an integer greater than or equal to one, b) aninitial subframe allocation offset i, wherein i is an integer greaterthan or equal to zero, and c) an initial subframe allocation bitmapindicating an initial plurality of subframes in k frames, wherein k isan integer and 1≦k≦n. The bitmap may apply to subframes in k framesstarting from frames whose SFN meets SFN mod n=i criterion. The initialplurality of subframes may comprise an initial plurality of specialsubframes.

After an increase or decrease in the number of the plurality of wirelessdevices or after an increase or decrease in the traffic load of thefirst base station by an amount greater than a load value, the firstbase station may transmit a second message. The second message maycomprise at least one of the following: a) the initial subframeallocation repetition period, b) the initial subframe allocation offset,and an updated subframe allocation bitmap indicating a second pluralityof subframes. The second plurality of subframes may comprise an updatedplurality of special subframes. The updated plurality of specialsubframes may comprise a smaller or greater number (respectivelycorresponding to increase or decrease in the number of wireless devicesor the traffic load) of special subframes than the initial plurality ofspecial subframes. During most symbols of a special subframe of a basestation, no signal may be transmitted by the base station or signals maybe transmitted with substantially lower power compared with transmitpower of signals transmitted during a subframe which is not assigned asa special subframe.

According to some of the various aspects of embodiments, a first basestation may transmit a first message to a first plurality of wirelessdevices in connected mode. The first message may comprise an initialfirst subframe allocation bitmap indicating an initial first pluralityof subframes. The initial first plurality of subframes may comprise aninitial first plurality of special subframes. Each of at least onesecond base station may transmit a second message to a second pluralityof wireless devices in connected mode. For each of the at least onesecond base station, the second message may comprise an initial secondsubframe allocation bitmap indicating an initial second plurality ofsubframes. The initial second plurality of subframes may comprise aninitial second plurality of special subframes. There may be a coverageoverlap between the first base station and each of the at least onesecond base station.

After an increase or decrease in the number of the plurality of wirelessdevices or after an increase or decrease in the traffic load of thefirst base station by an amount greater than a load value, the firstbase station may transmit a third message. The third message maycomprise an updated first subframe allocation bitmap indicating anupdated first plurality of subframes. The updated first plurality ofsubframes may comprise an updated first plurality of special subframes.The updated first plurality of special subframes may comprise a smalleror greater number (respectively corresponding to increase or decrease inthe number of wireless devices or the traffic load) of special subframesthan the initial first plurality of special subframes. Each of the atleast one second base station may transmit a fourth message. For each ofthe at least one second base station, the fourth message may comprise anupdated second subframe allocation bitmap indicating an updated secondplurality of subframes. The updated second plurality of subframes maycomprise an updated second plurality of special subframes. The updatedsecond plurality of special subframes may comprise a greater or smallernumber (respectively corresponding to increase or decrease in the numberof wireless devices or the traffic load) of special subframes than theinitial second plurality of special subframes. During most symbols of aspecial subframe of a base station, no signal may be transmitted by thebase station or signals may be transmitted with substantially lowerpower compared with transmit power of signals transmitted during asubframe which is not assigned as a special subframe (called non-specialsubframes or regular subframes).

According to some of the various aspects of embodiments, a networkcomprises a plurality of base stations. Transmission time may be dividedinto a plurality of frames. Each frame in the plurality of frames may beassigned a system frame number (SFN) and may be further divided into Nsubframes. N is an integer greater than one. A first base station maytransmit a first message to a first plurality of wireless devices inconnected mode. The first message may comprise at least one of thefollowing: a) an initial first subframe allocation repetition period interms of n frames, wherein n is an integer greater than or equal to one,b) an initial first subframe allocation offset i, wherein i is aninteger greater than or equal to zero, and c) an initial first subframeallocation bitmap indicating an initial first plurality of subframes ink frames, wherein k is an integer and 1≦k≦n. The bitmap may apply tosubframes in k frames starting from frames whose SFN meets (SFN mod n=i)criterion. The initial first plurality of subframes may comprise aninitial first plurality of special subframes.

Each of at least one second base station may transmit a second messageto a second plurality of wireless devices in connected mode. For each ofthe at least one second base station, the second message may comprise atleast one of the following: a) the initial first subframe allocationrepetition period, b) the initial first subframe allocation offset, andc) an initial second subframe allocation bitmap indicating an initialsecond plurality of subframes. The initial second plurality of subframesmay comprise an initial second plurality of special subframes. There isa coverage overlap between the first base station and each of the atleast one second base station.

After an increase or decrease in the number of the plurality of wirelessdevices or after an increase or decrease in the traffic load of thefirst base station by an amount greater than a load value, the firstbase station may transmit a third message. The third message maycomprise an updated first subframe allocation bitmap indicating anupdated first plurality of subframes. The updated first plurality ofsubframes may comprise an updated first plurality of special subframes.The updated first plurality of special subframes may comprise a smalleror greater number (respectively corresponding to increase or decrease inthe number of wireless devices or the traffic load) of special subframesthan the initial first plurality of special subframes.

Each of the at least one second base station may transmit a fourthmessage. For each of the at least one second base station, the fourthmessage may comprise an updated second subframe allocation bitmapindicating an updated second plurality of subframes. The updated secondplurality of subframes may comprise an updated second plurality ofspecial subframes. The updated second plurality of special subframes maycomprise a greater or smaller (respectively corresponding to increase ordecrease in the number of wireless devices or the traffic load) numberof special subframes than the initial second plurality of specialsubframes. During most symbols of a special subframe of a base station,no signal may be transmitted by the base station or signals may betransmitted with substantially lower power compared with transmit powerof signals transmitted during a subframe which is not assigned as aspecial subframe. In a special subframe, a base station transmits acommon reference signal only in a control region of the specialsubframe.

Example embodiments enable dynamic configuration of special subframesand dynamic adaptation of special subframes in one or more base stationsto adapt to changes in the traffic load of one or more base stations.Such a dynamic configuration may increase air interface and backhauloverhead. Additional overhead in signaling may include additional RRCmessages and additional X2 application protocol messages. The gains inair interface efficiency maybe due to reduction in the special subframesin some of the cells with relatively high load. This may reduce thepacket congestion in those cells and reduce packet transmission delayand/or packet loss and may increase cell throughput. Some of the networksimulations/analysis shows that the benefits in air interface efficiencygains may be more than the negative impact due to additional overhead.The example embodiments may add additional complexity in networkoperations, but instead it may increase the overall spectral efficiencyin the network. The dynamic operation may be triggered when the load isdecreased by an amount greater than a load value or decreases by anamount greater than a load value. Therefore, the operation may beperformed selectively, by one or more base stations, and may becommunicated to one or more other base stations. This dynamicconfiguration is different from other methods employed to increase cellcapacity. It may require transmission and reception of additional RRCreconfiguration messages to reconfigure the air interface parameters inwireless devices in the coverage area and may require transmission andreception of additional X2 interface messages to other base stations.

The third message and the fourth message may comprise the initial firstsubframe allocation repetition period and the initial first subframeallocation offset. Base stations in the plurality of second basestations may configure the same set of subframes as the second initialplurality of special subframes. Base stations in the plurality of secondbase stations may configure the same set of subframes as the secondupdated plurality of special subframes. n may be equal to 2′, wherein jis one of the following numbers: 0, 1, 2, 3, 4, and 5. i may be one ofthe following numbers: 0, 1, 2, 3, 4, 5, 6, and 7 and i may be smallerthan n. k may be equal to one or four. N may be equal to ten. Each basestation in the plurality of base stations may comprise at least onecarrier.

Each base station in the plurality of base stations may broadcast thesystem frame number represented by m bits. Each base station in theplurality of base stations may broadcast the most significant bits ofthe system frame number using a plurality of subcarriers in the in themiddle of the frequency band of a carrier on the first subframe of eachframe in the plurality of frames in a field in a physical broadcastchannel. m may be equal to 10. p may be equal to 8. Each base station inthe plurality of base stations may broadcast implicitly the m−p leastsignificant bits of the system frame number by coding the physicalbroadcast channel over 2^((m-p)) frames. The timing of the codedphysical broadcast channel may determine the m−p least significant bits.Each base station in the plurality of base stations may broadcast thesame system frame number if the frames are transmitted substantially atthe same time. The (m−p) least significant bits of the system framenumber may be broadcast by encoding control blocks in the physicalbroadcast channel over 2^((m-p)) frames. Sequential position of theencoded control blocks determining the (m−p) least significant bits.

For an FDD network, special subframes may be a subset of subframesconsisting of subframes number one, two, three, six, seven, and eight ineach frame, wherein subframe numbers in each frame start from numberzero. For a TDD network, special subframes may be a subset of subframesconsisting of subframes number three, four, seven, eight and nine ineach frame, wherein subframe numbers in each frame start from numberzero. The first message, the second message, and the fourth message maybe broadcasted using physical downlink shared channel.

The first message, the second message, and the fourth message may bebroadcasted using system information blocks. A base station in theplurality of base stations may not transmit unicast data in a subframethat is assigned by the base station as the special subframe. A basestation in the plurality of base stations may not transmit unicast datato a release 8 or 9 LTE wireless device in a subframe that is assignedby the base station as the special subframe.

The first base station may transmit a plurality of unicast messages to asubset of the first plurality of wireless devices. The plurality ofunicast messages may configure at least one of the following: a)measurement subframes of a primary carrier for the subset of the firstplurality of wireless devices, and b) measurement subframes of aplurality neighboring carriers for the subset of the first plurality ofwireless devices. The traffic carried by the first base station mayincrease, when the number of the first plurality of wireless devicesincreases. Traffic load of the first base station may increase, when thenumber of the first plurality of wireless devices increases.

There may be an X2 interface between the first base station and each ofthe second plurality of base stations. After an increase in the numberof the first plurality of wireless devices, the first base station maytransmit a message to each of the at least one second base station. Themessage may comprise a first pattern bitmap indicating the updated firstspecial subframe allocation. The message may further comprise a secondpattern bitmap indicating a subset of the special subframes indicated bythe first pattern bitmap used to configure measurement parameters for asubset of the second plurality of wireless devices. Each of the at leastone second base station may acknowledge the receipt of the message.

The first base station may have a substantially higher transmit powerthan each of the at least one second base station. The updated firstplurality of special subframes may be a subset of the initial firstplurality of special subframes. The initial second plurality of specialsubframes may be a subset of the updated second plurality of specialsubframes. Each of the plurality of second base stations may configurethe initial and updated second plurality of special subframes based onmessages received from the first base station on an X2 interface betweenthe first base station and each of the plurality of second basestations. The first plurality of subframes may further comprisesubframes used for broadcasting or multicasting, or subframes used forscheduling LTE release 10 and beyond devices.

The second plurality of subframes may further comprise subframes usedfor broadcasting or multicasting, or subframes used for scheduling LTErelease 10 or beyond wireless devices. The initial first subframeallocation bitmap, the updated first subframe allocation bitmap, theinitial second subframe allocation bitmap, and the updated secondsubframe allocation bitmap may be 6 bits or 24 bits long. An example ofspecial subframes is almost blank subframe.

A network may comprise a plurality of base stations. A first basestation may transmit radio signals at a substantially different powerthan a plurality of second base stations. This may result in the firstbase station being in a different power class. The first base stationmay be of a different base station type than the second base stations.The base station type, for example, may be one of the following: femtobase station type, pico base station type, micro base station type,macro base station type, relay type, and/or the like. Transmission timemay be divided into a plurality of frames, and each frame in theplurality of frames may further be divided into a plurality ofsubframes. Each of the plurality of second base stations and the firstbase station may provide overlapping coverage in at least a region inthe service area of the network. In an example embodiment, each of theplurality of second base stations may configure a second plurality ofspecial subframes. During the majority of (most) symbols of a specialsubframe of a base station, no signal may be transmitted by the basestation or signals may be transmitted with substantially lower powercompared with transmit power of signals transmitted during a subframewhich is not assigned as a special subframe. The base stations in theplurality of second base stations may configure the same set ofsubframes as the second plurality of special subframes.

According to some of the various aspects of embodiments, each of theplurality of second base stations may transmit a second message to asecond plurality of wireless devices in connected mode. For each of theplurality of second base stations, the second message may comprise asecond subframe allocation bitmap indicating a second plurality ofsubframes. The second plurality of subframes may comprise a secondplurality of special subframes. During most symbols of a specialsubframe of a base station, no signal may be transmitted by the basestation or signals may be transmitted with substantially lower powercompared with transmit power of signals transmitted during a subframewhich is not assigned as a special subframe (may be called non-specialsubframes or regular subframes). The base stations in the plurality ofsecond base stations may configure the same set of subframes as thesecond plurality of special subframes.

According to some of the various aspects of embodiments, the first basestation may transmit a first message to a first plurality of wirelessdevices in connected mode. The first message may comprise a firstsubframe allocation bitmap indicating a first plurality of subframes.The first plurality of subframes may comprise a first plurality ofspecial subframes. Each of the plurality of second base stations maytransmit a second message to a second plurality of wireless devices inconnected mode. For each of the plurality of second base stations, thesecond message may comprise a second subframe allocation bitmapindicating a second plurality of subframes. The second plurality ofsubframes may comprise a second plurality of special subframes. All thebase stations in the plurality of second base stations may configure thesame set of subframes as the second plurality of special subframes.During most symbols of a special subframe of a base station, no signalmay be transmitted by the base station or signals may be transmittedwith substantially lower power compared with transmit power of signalstransmitted during a subframe which is not assigned as a specialsubframe. The first plurality of special subframes and the secondplurality of special subframes may not substantially overlap in time(may be two sets of disjoint subframes or equally may not share the samesubframe).

According to some of the various aspects of embodiments, each of theplurality of second base stations may transmit a second message to asecond plurality of wireless devices in connected mode. For each of theplurality of second base stations, the second message may comprise atleast one of the following: a) a second subframe allocation repetitionperiod in terms of n frames, wherein n is an integer greater than orequal to one, b) a second subframe allocation offset, i, wherein i is aninteger greater than or equal to zero, and c) a second subframeallocation bitmap indicating a second plurality of subframes in kframes, wherein k is an integer and 1≦k≦n. The bitmap may apply tosubframes in k frames starting from frames whose SFN meets SFN mod n=icriterion. The second plurality of subframes may comprise a secondplurality of special subframes. During most symbols of a specialsubframe of a base station, no signal may be transmitted by the basestation or signals may be transmitted with substantially lower powercompared with transmit power of signals transmitted during a subframewhich is not assigned as a special subframe. The base stations in theplurality of second base stations may configure the same second subframeallocation repetition period, the same second subframe allocationoffset, and the same set of subframes as the second plurality of specialsubframes.

According to some of the various aspects of embodiments, transmissiontime may be divided into a plurality of frames, and each frame in theplurality of frames may be assigned a system frame number (SFN) and mayfurther be divided into N subframes. N is an integer greater than one.The first base station may transmit a first message to a first pluralityof wireless devices in connected mode. The first message may comprise atleast one of the following: a) a first subframe allocation repetitionperiod in terms of n frames, wherein n is an integer greater than orequal to one, b) a first subframe allocation offset, i, wherein i is aninteger greater than or equal to zero, and c) a first subframeallocation bitmap indicating a first plurality of subframes in k frames,wherein k is an integer and 1≦k≦n. The bitmap may apply to subframes ink frames starting from frames whose SFN meets SFN mod n=i criterion. Thefirst plurality of subframes may comprise a first plurality of specialsubframes.

Each of the plurality of second base stations may transmit a secondmessage to a second plurality of wireless devices in connected mode. Foreach of the plurality of second base stations, the second message maycomprise at least one of the following: a) the first subframe allocationrepetition period, b) the first subframe allocation offset, and c) asecond subframe allocation bitmap indicating a second plurality ofsubframes. The second plurality of subframes may comprise a secondplurality of special subframes. All the base stations in the pluralityof second base stations may configure the same set of subframes as thesecond plurality of special subframes. During most symbols of a specialsubframe of a base station, no signal may be transmitted by the basestation or signals may be transmitted with substantially lower powercompared with transmit power of signals transmitted during a subframewhich is not assigned as a special subframe. The first plurality ofspecial subframes and the second plurality of special subframes may bedisjoint.

Example embodiments enable configuration of special subframes in one ormore base stations. Changes in special subframe allocation in one basestation may result in changes in special subframe allocation of aplurality of base stations. Such a configuration may increase airinterface and backhaul overhead. Additional overhead in signaling mayinclude additional RRC messages and additional X2 application protocolmessages. The gains in air interface efficiency maybe due to reductionin inter-cell interference in the network. This may reduce interferenceand may reduce packet loss and may increase cell throughput. Some of thenetwork simulations/analyses show that the benefits in air interfaceefficiency gains may be more than the negative impact due to additionaloverhead. The example embodiments may add additional complexity innetwork operations; instead it may increase the overall spectralefficiency in the network. Novel constraints are introduced in specialsubframe allocation among base stations of different types. A change inspecial subframe allocation of a high power base station may becommunicated to many other low power base stations. Requiredcommunications between base stations are introduced to satisfy theseconstraints. These novel constraints and required communications mayincrease network complexity; instead they may increase networkperformance. Therefore, the operation may be performed selectively, byone or more base stations, and may be communicated to one or more otherbase stations. This dynamic configuration is different from othermethods employed to increase cell capacity. It may require transmissionand reception of additional RRC reconfiguration messages to reconfigurethe air interface parameters in wireless devices in the coverage areaand may require transmission and reception of additional X2 interfacemessages to other base stations.

In a special subframe, a base station may transmit a common referencesignal only in a control region of the special subframe. n may be equalto 2^(j), wherein j is one of the following numbers: 0, 1, 2, 3, 4, and5. i may be one of the following numbers: 0, 1, 2, 3, 4, 5, 6, and 7. imay be smaller than n. k may be equal to one or four. N may be equal toten. Each base station in the plurality of base stations may comprise atleast one carrier. Each base station in the plurality of base stationsmay broadcast the system frame number represented by m bits. Each basestation in the plurality of base stations may broadcast the p mostsignificant bits of the system frame number using a plurality ofsubcarriers in the in the middle of the frequency band of a carrier onthe first subframe of each frame in the plurality of frames in a fieldin a physical broadcast channel. m may be equal to 10. p may be equal to8. Each base station in the plurality of base stations may broadcastimplicitly the m−p least significant bits of the system frame number bycoding the physical broadcast channel over 2^((m-p)) frames. The timingof the coded physical broadcast channel may determine the m−p leastsignificant bits. Each base station in the plurality of base stationsmay broadcast the same system frame number if the frames are transmittedsubstantially at the same time. The (m−p) least significant bits of thesystem frame number may be broadcast by encoding control blocks in thephysical broadcast channel over 2^((m-p)) frames. Sequential position ofthe encoded control blocks determining the (m−p) least significant bits.

In a FDD system, special subframes may be a subset of subframesconsisting of subframes number one, two, three, six, seven, and eight ineach frame. Subframe numbers in each frame start from number zero. In aTDD system, special subframes may be a subset of subframes consisting ofsubframes number three, four, seven, eight and nine in each frame.Subframe numbers in each frame start from number zero. The first messageand the second message may be broadcasted using physical downlink sharedchannel. The first message and the second message may be broadcastedusing system information blocks. A base station in the plurality of basestations may not transmit unicast data in a subframe that is assigned bythe base station as the special subframe. A base station in theplurality of base stations may not transmit unicast data to a release 8or 9 LTE wireless device in a subframe that is assigned by the basestation as the special subframe. A base station may transmit a pluralityof unicast messages to a subset of the first plurality of wirelessdevices. The plurality of unicast messages may configure: a) measurementsubframes of a primary carrier for the subset of the first plurality ofwireless devices, or b) measurement subframes of a plurality neighboringcarriers for the subset of the first plurality of wireless devices.

After an increase in the number of the first plurality of wirelessdevices by an amount greater than a load value, the first base stationmay decrease the number of special subframes in the first plurality ofspecial subframes. After a decrease in the number of the first pluralityof wireless devices by an amount greater than a load value, the firstbase station may increase the number of special subframes in the firstplurality of special subframes. After an increase in the traffic load ofthe first base station by an amount greater than a load value, the firstbase station may decrease the number of special subframes in the firstplurality of special subframes. After a decrease in the traffic load ofthe first base station by an amount greater than a load value, the firstbase station may increase the number of special subframes in the firstplurality of special subframes. The traffic carried by the first basestation may increase, when the number of the first plurality of wirelessdevices increases. Traffic load of the first base station may increase,when the number of the first plurality of wireless devices increases.

There may be an X2 interface between the first base station and each ofthe second plurality of base stations. The first base station maytransmit a message to each of the at least one second base station. Themessage may comprise a first pattern bitmap indicating the first specialsubframe allocation. The message may further comprise a second patternbitmap indicating a subset of the special subframes indicated by thefirst pattern bitmap used to configure measurement parameters for asubset of the second plurality of wireless devices. Each of the at leastone second base station acknowledges the receipt of the message. Thefirst base station has a substantially higher transmit power than eachof the plurality of second base stations.

Frame and subframe transmission of the first base station and each ofthe second plurality of base stations may be substantially synchronized.Each of the plurality of second base stations may configure the secondplurality of special subframes based on messages received from the firstbase station on an X2 interface between the first base station and eachof the plurality of second base stations. The first plurality ofsubframes may further comprise subframes used for broadcasting ormulticasting, or subframes used for scheduling LTE release 10 and beyondwireless devices. The second plurality of subframes may further comprisesubframes used for broadcasting or multicasting, or subframes used forscheduling LTE release 10 or beyond wireless devices. The first subframeallocation bitmap and the second subframe allocation bitmap may be 6bits or 24 bits long. An example of special subframes is almost blanksubframes.

A network comprises a plurality of base stations. Transmission time maybe divided into a plurality of frames. Each frame in the plurality offrames may be assigned a system frame number (SFN). In an exampleembodiment, each base station in the plurality of base stations, in eachframe, may transmit the system frame number. Each base station in theplurality of base stations, in each frame, may transmit asynchronization signal indicating a cell ID. The transmission of thesynchronization signals may be substantially time aligned among theplurality of base stations. Transmission of the synchronization signalof each base station in the plurality of base stations are substantiallytime aligned with transmission of other synchronization signals of otherbase stations in the plurality of base station. All the base stations inthe plurality of base stations may transmit the same system frame numberin frames that are transmitted substantially at the same time. In anexample embodiment, the term substantially may be employed to show thatthe synchronization may not be perfect due to inherent synchronizationerrors or inaccuracy in the synchronization mechanism.

In this disclosure, phrases such as “each base station in a plurality ofbase stations,” “all base station in a plurality of base stations,” orthe like refer to select base stations that are similarly configured ina group of base stations. It is possible that there may be more basestations in a network that are configured to perform differently. Inthose cases, the phrases do not necessarily include those differentlyconfigured base stations. Additionally, similar phrases that refer toother devices such as wireless devices, etc. may also have a similarinterpretation. For example, in a give network, there may be a basestation in the network that is not synchronized with other basestations, and therefore may not be considered in the set of theplurality of base stations.

According to some of the various aspects of embodiments, each frame inthe plurality of frames may be assigned a system frame number (SFN).Each frame may be further divided into a plurality of subframes. Eachbase station in the plurality of base stations, in each frame, maytransmit the system frame number. Each base station in the plurality ofbase stations, in each frame, may transmit a synchronization signalindicating a cell (carrier) ID. The transmission of the synchronizationsignals may be substantially time aligned among the plurality of basestations. The base stations transmitting in substantial time alignmentduring each frame in the plurality of frames, a synchronization signalindicating a cell ID.

Each base station in the plurality of base stations may transmit amessage to a plurality of wireless devices in connected mode. For eachof the plurality of base stations, the message may comprise at least oneof: a) a subframe allocation repetition period in terms of p frames,wherein p is an integer greater than or equal to one, b) a subframeallocation offset i, wherein i is an integer greater than or equal tozero, and c) a subframe allocation bitmap indicating a plurality ofsubframes in k frames, wherein k is an integer and 1≦k≦p. The bitmap mayapply to subframes in k frames starting from frames whose SFN meets SFNmod p=i criterion. The plurality of subframes may comprise a pluralityof special subframes. During most symbols of a special subframe of abase station, no signal may be transmitted by the base station orsignals may be transmitted with substantially lower power compared withtransmit power of signals transmitted during a subframe which is notassigned as a special subframe. All the base stations in the pluralityof base stations may transmit the same system frame number in framesthat are transmitted substantially at the same time.

According to some of the various aspects of embodiments, each frame inthe plurality of frames may be assigned a system frame number (SFN)represented by m bits. Each frame may further be divided into aplurality of N subframes, wherein N is an integer greater than one. Eachbase station in the plurality of base stations, in each frame, maytransmit the n most significant bits of the system frame number using aplurality of OFDM subcarriers in the in the middle of the frequency bandof a carrier on the first subframe of each frame in the plurality offrames in a field in a physical broadcast channel. Each base station inthe plurality of base stations, in each frame, may transmit implicitlythe m−n least significant bits of the system frame number by coding thephysical broadcast channel over 2^((m-n)) frames. The timing of thecoded physical broadcast channel may determine the m−n least significantbits. Each base station in the plurality of base stations may transmit asynchronization signal indicating a cell ID. The transmission of thesynchronization signals are substantially time aligned among theplurality of base stations. All the base stations in the plurality ofbase stations may transmit the same system frame number in frames thatare transmitted substantially at the same time.

According to some of the various aspects of embodiments, each frame inthe plurality of frames may be assigned a system frame number (SFN)represented by m bits. Each frame may further be divided into aplurality of N subframes, wherein N is an integer greater than one. Eachbase station in the plurality of base stations, in each frame, maytransmit the n most significant bits of the system frame number using aplurality of OFDM subcarriers in the in the middle of the frequency bandof a carrier on the first subframe of each frame in the plurality offrames in a field in a physical broadcast channel. Each base station inthe plurality of base stations, in each frame, may transmit implicitlythe m−n least significant bits of the system frame number by coding thephysical broadcast channel over 2^((m-n)) frames. The timing of thecoded physical broadcast channel determines the m−n least significantbits.

Each base station in the plurality of base stations, in each frame, maytransmit a synchronization signal indicating a cell ID. The transmissionof the synchronization signals are substantially time aligned among theplurality of base stations. Each base station in the plurality of basestations may transmit a message to a plurality of wireless devices inconnected mode. For each of the plurality of base stations, the messagemay comprise at least one of the following: a) a subframe allocationrepetition period in terms of p frames, wherein p is an integer greaterthan or equal to one, b) a subframe allocation offset, i, wherein i isan integer greater than or equal to zero, and c) a subframe allocationbitmap indicating a plurality of subframes in k frames, wherein k is aninteger and 1≦k≦p. The bitmap may apply to subframes in k framesstarting from frames whose SFN meets SFN mod p=i criterion. Theplurality of subframes may comprise a plurality of special subframes.During most symbols of a special subframe of a base station, no signalmay be transmitted by the base station or signals may be transmittedwith substantially lower power compared with transmit power of signalstransmitted during a subframe which is not assigned as a specialsubframe. All the base stations in the plurality of base stations maytransmit the same system frame number in frames that are transmittedsubstantially at the same time.

A base station, in a special subframe, may transmit a common referencesignal only in a control region of the special subframe. p may be equalto 2^(j), wherein j is one of the following numbers: 0, 1, 2, 3, 4, and5. i may be one of the following numbers: 0, 1, 2, 3, 4, 5, 6, and 7. imay be smaller than p. k may be equal to one or four. N may be equal toten. The base station may comprise at least one carrier. m may be equalto 10. n may be equal to 8. The message may be transmitted usingphysical downlink shared channel. The message may be broadcasted usingsystem information blocks. The base station may not transmit unicastdata in a subframe that is assigned by the base station as the specialsubframe. The base station may not transmit unicast data to a release 8or 9 LTE wireless device in a subframe that is assigned by the basestation as the special subframe.

After an increase in the number of the plurality of wireless devices byan amount greater than a load value, the base station may decrease thenumber of special subframes in the plurality of special subframes. Aftera decrease in the number of the plurality of wireless devices by anamount greater than a load value, the base station may increase thenumber of special subframes in the plurality of special subframes. Afteran increase in the traffic load of the base station by an amount greaterthan a load value, the base station may decrease the number of specialsubframes in the plurality of special subframes. After a decrease in thetraffic load of the base station by an amount greater than a load value,the base station may increase the number of special subframes in theplurality of special subframes. The traffic carried by the base stationmay increase, when the number of the plurality of wireless devicesincreases. Traffic load of the base station may increase, when thenumber of the plurality of wireless devices increases.

The subframe allocation bitmap may be 6 bits or 24 bits long. Thesynchronization signal may comprise a primary synchronization signal anda secondary synchronization signal. The primary synchronization signalmay be generated using a frequency-domain Zadoff-Chu sequence. Theprimary synchronization signal may be mapped to the last OFDM symbol inslots 0 and 10 for FDD frame structure. The primary synchronizationsignal may be mapped to the third OFDM symbol in subframes 1 and 6 forTDD frame structure. The secondary synchronization signal may begenerated using an interleaved concatenation of two length-31 binarysequences. The concatenated sequence may be scrambled with a scramblingsequence given by the primary synchronization signal. The secondarysynchronization signal may differ between subframe 0 and subframe 5. Thefirst plurality of subframes may further comprise subframes used forbroadcasting or multicasting, or subframes used for scheduling LTErelease 10 and beyond wireless devices. An example of special subframesis almost blank subframes.

Example embodiments enable synchronized transmission among the basestations. In an example embodiment, not only frame transmissions aresubstantially synchronized among different base stations, but alsosystem frame number transmissions are synchronized among different basestations. The same system frame number is transmitted during framestransmitted substantially synchronously. Different cells of the samebase station and different cells belonging to different base stationsmay transmit the same system frame number during the same frame that istransmitted substantially at the same time. Example embodiments, amongother things, may enable an efficient configuration of special subframesin one or more base stations and/or may enable a more efficientinter-cell interference management. Such a complex synchronization amongcells of the same base station and cells belonging to different basestations may increase backhaul overhead and network complexity.Additional complexity in network architecture may include additionalmechanisms for frame synchronization among different base stations aswell as mechanisms for synchronization in transmitting the same systemframe number during synchronized frames. GPS assisted or packet basedsynchronization mechanisms may be enhanced to include SFNsynchronization among the base stations. The gains in air interfaceefficiency maybe due to reduction in inter-cell interference. This mayreduce the packet loss and may increase cell throughput. Some of thenetwork simulations/analysis shows that the benefits in air interfaceefficiency gains may be more than the negative impact due to additionalnetwork complexity and overhead. The example embodiments may addadditional complexity in network operations, but instead it may increasethe overall spectral efficiency in the air interface. The synchronizedoperation may be triggered if the advantages in SFN synchronization ismore beneficial compared to disadvantages due to the additional networkcomplexity. Therefore, the operation may be performed selectively, byone or more base stations. This synchronized configuration is differentfrom other network synchronization methods employed in, for example, TDDsystems. It may require transmission and reception of additionalmessages to ensure synchronization in system frame number transmission(the same number is transmitted during the simultaneous frames ofdifferent base stations). This mechanism may require transmission andreception of additional X2 and/or S1 interface messages or additionalGPS assisted mechanisms.

In an example embodiment, a system frame number coordinator maycoordinate the transmission of the same system frame number in frames ofdifferent base stations. Control messages may trigger multiple basestations to start or re-start the SFN transmission at the same timestarting from the same initial number. This mechanism requiresadditional complexity compared with transmission of the same SFN inframes of different cells of the same base station, since it requiresprotocols/mechanisms for coordination among many base stations. When anew base station is added to the network, additional mechanisms may berequired to communicate with the new base station and ensure that thenew base station transmits the same system frame number along with otherbase stations in the network. This may be achieved via control messagestransmitted via X2 and/or S1 interface. In an example embodiment, asystem frame number coordinator may communicate/transmit messages to theexisting and new base stations to synchronize SFN transmission.Distributed algorithms and/or GPS bases algorithms may also be developedto ensure SFN synchronization among base stations.

A network comprises a plurality of base stations. A first base stationmay transmit radio signals at a substantially different power than aplurality of second base stations and a plurality of third basestations. This may result in the first base station being in a differentpower class than the plurality of second base stations and the pluralityof third base stations. In other words, the first base station may be ofa different base station type than the plurality of second base stationsand the plurality of third base stations. Transmission time may bedivided into a plurality of frames. Each frame in the plurality offrames may further be divided into a plurality of subframes. Each of theplurality of second base stations and the first base station may provideoverlapping coverage in at least a region in the service area of thenetwork. Each of the plurality of third base stations and the first basestation may provide overlapping coverage in at least a region in theservice area of the network. In the specification, an example of specialsubframe may be the almost blank subframe. According to some of thevarious aspects of embodiments, each of the plurality of second basestations may allow regular access to wireless devices subscribed to thenetwork. Each of the plurality of second base stations may configure asecond plurality of special subframes. The base stations in theplurality of second base stations may configure the same set ofsubframes as the second plurality of special subframes. Each of theplurality of third base stations, may allow regular access to only arestricted subset of wireless devices subscribed to the network, and mayreject regular access to other subscribers or allow a lower priorityaccess. Each of the plurality of third base stations, may configure athird plurality of special subframes. At least two base stations in theplurality of third base stations may identify different set of subframesas the second plurality of special subframes. The regular access may bethe access that is due to subscription of a device in the network. Inone example embodiment, for example, guest access, access with lowpriority, or access with no guaranteed QoS, and/or the like may not beconsidered a regular access. During most symbols of a special subframeof a base station, no signal may be transmitted by the base station orsignals may be transmitted with substantially lower power compared withtransmit power of signals transmitted during a subframe which is notassigned as a special subframe.

According to some of the various aspects of embodiments, each of theplurality of second base stations may allow regular access to wirelessdevices subscribed to the network. Each of the plurality of second basestations may transmit a second message to a second plurality of wirelessdevices in connected mode. For each of the plurality of second basestations, the second message may comprise a second subframe allocationbitmap indicating a second plurality of subframes. The second pluralityof subframes may comprise a second plurality of special subframes. Thebase stations in the plurality of second base stations may configure thesame set of subframes as the second plurality of special subframes. Eachof the plurality of third base stations may allow regular access to onlya restricted subset of wireless devices subscribed to the network. Eachof the plurality of third base stations may transmit a third message toa third plurality of wireless devices in connected mode. For each of theplurality of third base stations, the third message may comprise a thirdsubframe allocation bitmap indicating a third plurality of subframes.The third plurality of subframes may comprise a third plurality ofspecial subframes. At least two base stations in the plurality of thirdbase stations configure different sets of subframes as the secondplurality of special subframes. During most symbols of a specialsubframe of a base station, no signal may be transmitted by the basestation or signals may be transmitted with substantially lower powercompared with transmit power of signals transmitted during a subframewhich is not assigned as a special subframe.

According to some of the various aspects of embodiments, the first basestation may transmit a first message to a first plurality of wirelessdevices in connected mode. The first message may comprise a firstsubframe allocation bitmap indicating a first plurality of subframes.The first plurality of subframes may comprise a first plurality ofspecial subframes. Each of the plurality of second base stations mayallow regular access to wireless devices subscribed to the network. Eachof the plurality of second base stations may transmit a second messageto a second plurality of wireless devices in connected mode. For each ofthe plurality of second base stations, the second message may comprise asecond subframe allocation bitmap indicating a second plurality ofsubframes. The second plurality of subframes may comprise a secondplurality of special subframes. The base stations in the plurality ofsecond base stations may configure the same set of subframes as thesecond plurality of special subframes. The first plurality of specialsubframes and the second plurality of special subframes may notsubstantially overlap in time (may be two sets of disjoint subframes orequally may not share the same subframe).

Each of the plurality of third base stations may allow regular access toonly a restricted subset of wireless devices subscribed to the network.Each of the plurality of third base stations may transmit a thirdmessage to a third plurality of wireless devices in connected mode. Foreach of the plurality of third base stations, the third message maycomprise a third subframe allocation bitmap indicating a third pluralityof subframes. The third plurality of subframes may comprise a thirdplurality of special subframes. At least two base stations in theplurality of third base stations may not configure the same set ofsubframes as the second plurality of special subframes. During mostsymbols of a special subframe of a base station, no signal may betransmitted by the base station or signals may be transmitted withsubstantially lower power compared with transmit power of signalstransmitted during a subframe which is not assigned as a specialsubframe.

According to some of the various aspects of embodiments, the first basestation may transmit a first message to a first plurality of wirelessdevices in connected mode. The first message may comprise a firstsubframe allocation bitmap indicating a first plurality of subframes.The first plurality of subframes may comprise a first plurality ofspecial subframes. Each of the plurality of second base stations mayallow regular access to wireless devices subscribed to the network. Eachof the plurality of second base stations may transmit a second messageto a second plurality of wireless devices in connected mode. For each ofthe plurality of second base stations, the second message may compriseat least one of: a) a second subframe allocation repetition period interms of n frames, wherein n is an integer greater than or equal to one,b) a second subframe allocation offset, i, wherein i is an integergreater than or equal to zero, and c) a second subframe allocationbitmap indicating a second plurality of subframes in k frames, wherein kis an integer and 1≦k≦n. The bitmap may apply to subframes in k framesstarting from frames whose SFN meets SFN mod n=i criterion.

The second plurality of subframes may comprise a second plurality ofspecial subframes. The base stations in the plurality of second basestations may configure the same second subframe allocation repetitionperiod, the same second subframe allocation offset, and the same set ofsubframes as the second plurality of special subframes. The firstplurality of special subframes and the second plurality of specialsubframes are disjoint. Each of the plurality of third base stations mayallow regular access to only a restricted subset of wireless devicessubscribed to the network. Each of the plurality of third base stationsmay transmit a third message to a third plurality of wireless devices inconnected mode. For each of the plurality of third base stations, thethird message may comprise at least one of: the second special subframeallocation repetition period, the second special subframe allocationoffset, and a third subframe allocation bitmap indicating a thirdplurality of subframes. The third plurality of subframes may comprise athird plurality of special subframes. At least two base stations in theplurality of third base stations may configure (identify) different setsof subframes as the second plurality of special subframes. During mostsymbols of a special subframe of a base station, no signal may betransmitted by the base station or signals may be transmitted withsubstantially lower power compared with transmit power of signalstransmitted during a subframe which is not assigned as a specialsubframe.

According to some of the various aspects of embodiments, the firstmessage may further comprise the second special subframe allocationperiod and the second special subframe allocation offset. A basestation, in a special subframe, may transmit a common reference signalonly in a control region of the special subframe. n may be equal to2^(j), wherein j is one of the following numbers: 0, 1, 2, 3, 4, and 5.i may be one of the following numbers: 0, 1, 2, 3, 4, 5, 6, and 7. i maybe smaller than n. k may be equal to one or four. N may be equal to ten.

Each base station in the plurality of base stations comprises at leastone carrier. Each base station in the plurality of base stations maybroadcast the system frame number represented by m bits. Each basestation in the plurality of base stations may broadcast the p mostsignificant bits of the system frame number using a plurality ofsubcarriers in the in the middle of the frequency band of a carrier onthe first subframe of each frame in the plurality of frames in a fieldin a physical broadcast channel. m may be equal to 10. p may be equal to8. Each base station in the plurality of base stations may broadcastimplicitly the m−p least significant bits of the system frame number bycoding the physical broadcast channel over 2^((m-p)) frames, wherein thetiming of the coded physical broadcast channel determines the m−p leastsignificant bits. The (m−n) least significant bits of the system framenumber may be broadcast by encoding control blocks in the physicalbroadcast channel over 2^((m-n)) frames. Sequential position of theencoded control blocks determining the (m−n) least significant bits.

Each base station in the plurality of base stations may broadcast thesame system frame number if the frames are transmitted substantially atthe same time.

In a FDD system, special subframes may be a subset of subframesconsisting of subframes number one, two, three, six, seven, and eight ineach frame, wherein subframe numbers in each frame start from numberzero. In a TDD system, special subframes are a subset of subframesconsisting of subframes number three, four, seven, eight and nine ineach frame, wherein subframe numbers in each frame start from numberzero. The first message, the second message, and the third message maybe broadcasted using physical downlink shared channel. The firstmessage, the second message, and the third message may be broadcastedusing system information blocks. A base station in the plurality of basestations may not transmit unicast data in a subframe that is assigned bythe base station as the special subframe. A base station in theplurality of base stations may not transmit unicast data to a release 8or 9 LTE wireless device in a subframe that is assigned by the basestation as the special subframe. A base station may transmit a pluralityof unicast messages to a subset of the first plurality of wirelessdevices. The plurality of unicast messages may configure measurementsubframes of a primary carrier for the subset of the first plurality ofwireless devices, and/or measurement subframes of a pluralityneighboring carriers for the subset of the first plurality of wirelessdevices.

After an increase in the number of the first plurality of wirelessdevices, the first base station may decrease the number of specialsubframes in the first plurality of special subframes. After a decreasein the number of the first plurality of wireless devices, the first basestation may increase the number of special subframes in the firstplurality of special subframes. After an increase in the traffic load ofthe first base station, the first base station may decrease the numberof special subframes in the first plurality of special subframes. Aftera decrease in the traffic load of the first base station, the first basestation may increase the number of special subframes in the firstplurality of special subframes. The traffic carried by the first basestation may increase, when the number of the first plurality of wirelessdevices increases. Traffic load of the first base station may increase,when the number of the first plurality of wireless devices increases.

There may be an X2 interface between the first base station and each ofthe second plurality of base stations. The first base station maytransmit a message to each of the at least one second base station. Themessage may comprise a first pattern bitmap indicating the first specialsubframe allocation. The message may further comprise a second patternbitmap indicating a subset of the special subframes indicated by thefirst pattern bitmap used to configure measurement parameters for asubset of the second plurality of wireless devices. Each of the at leastone second base station acknowledges the receipt of the message.

The first base station may have a substantially higher transmit powerthan each of the plurality of second base stations and each of theplurality of third base stations. Frame and subframe transmission of thefirst base station and each of the second plurality of base stations andeach of the plurality of third base stations may be substantiallysynchronized. Each of the plurality of second base stations mayconfigure the second plurality of special subframes based on messagesreceived from the first base station on an X2 interface between thefirst base station and each of the plurality of second base stations.The third plurality of special subframes may be configured in each ofthe plurality of third base stations using an OAM system. The thirdplurality of special subframes may be configured in each of theplurality of third base stations using an X2 interface between each ofthe plurality of third base stations and the first base station. Each ofthe plurality of third base stations may broadcast a CSG indicator. Eachof the plurality of third base stations may broadcast a CSG identity.Each of the third plurality of wireless devices may be configured with aCSG white-list including the CSG identity of a base station in theplurality of third base stations. At least two base stations in thethird plurality of base stations may broadcast different CSG identities.The at least two base stations in the third plurality of base stationsmay not broadcast the same CSG identity. The at least two base stationsin the third plurality of base stations may provide overlapping coveragearea in at least a region in the service area of the network. The firstplurality of subframes may further comprise subframes used forbroadcasting or multicasting, or may further comprise subframes used forscheduling LTE release 10 or beyond wireless devices. The secondplurality of subframes may further comprise subframes used forbroadcasting or multicasting, or may comprise subframes used forscheduling LTE release 10 or beyond wireless devices. The first, secondand third subframe allocation bitmaps may be 6 bits or 24 bits long.

Example embodiments enable configuration of special subframes in one ormore base stations. Changes in special subframe allocation in one basestation may result in changes in special subframe allocation of aplurality of base stations. Such a configuration may increase airinterface and backhaul overhead. Additional overhead in signaling mayinclude additional RRC messages and additional X2 application protocolmessages. The gains in air interface efficiency maybe due to reductionin inter-cell interference in the network. This may reduce interferenceand may reduce packet loss and may increase cell throughput. Some of thenetwork simulations/analyses show that the benefits in air interfaceefficiency gains may be more than the negative impact due to additionaloverhead. The example embodiments may add additional complexity innetwork operations; instead it may increase the overall spectralefficiency in the network. Novel constraints are introduced in specialsubframe allocation among base stations of different types. A change inspecial subframe allocation of a high power base station may becommunicated to many other low power base stations. Among low power basestations, constraints applied on special subframe allocation of CSGcells is different than the constraints applied on special subframeallocation of non-CSG cells. Required communications between basestations are introduced to satisfy these constraints. These novelconstraints and required communications may increase network complexity;instead they may increase network performance. Therefore, the operationmay be performed selectively, by one or more base stations, and may becommunicated to one or more other base stations. This dynamicconfiguration is different from other methods employed to increase cellcapacity. It may require transmission and reception of additional RRCreconfiguration messages to reconfigure the air interface parameters inwireless devices in the coverage area and may require transmission andreception of additional X2 interface messages to other base stations.

According to some of the various aspects of embodiments, the packets inthe downlink may be transmitted via downlink physical channels. Thecarrying packets in the uplink may be transmitted via uplink physicalchannels. The baseband data representing a downlink physical channel maybe defined in terms of at least one of the following actions: scramblingof coded bits in codewords to be transmitted on a physical channel;modulation of scrambled bits to generate complex-valued modulationsymbols; mapping of the complex-valued modulation symbols onto one orseveral transmission layers; precoding of the complex-valued modulationsymbols on layer(s) for transmission on the antenna port(s); mapping ofcomplex-valued modulation symbols for antenna port(s) to resourceelements; and/or generation of complex-valued time-domain OFDM signal(s)for antenna port(s).

Codeword, transmitted on the physical channel in one subframe, may bescrambled prior to modulation, resulting in a block of scrambled bits.The scrambling sequence generator may be initialized at the start ofsubframe(s). Codeword(s) may be modulated using QPSK, 16QAM, 64QAM,128QAM, and/or the like resulting in a block of complex-valuedmodulation symbols. The complex-valued modulation symbols for codewordsto be transmitted may be mapped onto one or several layers. Fortransmission on a single antenna port, a single layer may be used. Forspatial multiplexing, the number of layers may be less than or equal tothe number of antenna port(s) used for transmission of the physicalchannel. The case of a single codeword mapped to multiple layers may beapplicable when the number of cell-specific reference signals is four orwhen the number of UE-specific reference signals is two or larger. Fortransmit diversity, there may be one codeword and the number of layersmay be equal to the number of antenna port(s) used for transmission ofthe physical channel.

The precoder may receive a block of vectors from the layer mapping andgenerate a block of vectors to be mapped onto resources on the antennaport(s). Precoding for spatial multiplexing using antenna port(s) withcell-specific reference signals may be used in combination with layermapping for spatial multiplexing. Spatial multiplexing may support twoor four antenna ports and the set of antenna ports used may be {0,1} or{0, 1, 2, 3}. Precoding for transmit diversity may be used incombination with layer mapping for transmit diversity. The precodingoperation for transmit diversity may be defined for two and four antennaports. Precoding for spatial multiplexing using antenna ports withUE-specific reference signals may also, for example, be used incombination with layer mapping for spatial multiplexing. Spatialmultiplexing using antenna ports with UE-specific reference signals maysupport up to eight antenna ports. Reference signals may be pre-definedsignals that may be used by the receiver for decoding the receivedphysical signal, estimating the channel state, and/or other purposes.

For antenna port(s) used for transmission of the physical channel, theblock of complex-valued symbols may be mapped in sequence to resourceelements. In resource blocks in which UE-specific reference signals arenot transmitted the PDSCH may be transmitted on the same set of antennaports as the physical broadcast channel in the downlink (PBCH). Inresource blocks in which UE-specific reference signals are transmitted,the PDSCH may be transmitted, for example, on antenna port(s) {5, {7},{8}, or {7, 8, . . . , v+6}, where v is the number of layers used fortransmission of the PDSCH.

Common reference signal(s) may be transmitted in physical antennaport(s). Common reference signal(s) may be cell-specific referencesignal(s) (RS) used for demodulation and/or measurement purposes.Channel estimation accuracy using common reference signal(s) may bereasonable for demodulation (high RS density). Common referencesignal(s) may be defined for LTE technologies, LTE-advancedtechnologies, and/or the like. Demodulation reference signal(s) may betransmitted in virtual antenna port(s) (i.e., layer or stream). Channelestimation accuracy using demodulation reference signal(s) may bereasonable within allocated time/frequency resources. Demodulationreference signal(s) may be defined for LTE-advanced technology and maynot be applicable to LTE technology. Measurement reference signal(s),may also called CSI (channel state information) reference signal(s), maybe transmitted in physical antenna port(s) or virtualized antennaport(s). Measurement reference signal(s) may be Cell-specific RS usedfor measurement purposes. Channel estimation accuracy may be relativelylower than demodulation RS. CSI reference signal(s) may be defined forLTE-advanced technology and may not be applicable to LTE technology.

In at least one of the various embodiments, uplink physical channel(s)may correspond to a set of resource elements carrying informationoriginating from higher layers. The following example uplink physicalchannel(s) may be defined for uplink: a) Physical Uplink Shared Channel(PUSCH), b) Physical Uplink Control Channel (PUCCH), c) Physical RandomAccess Channel (PRACH), and/or the like. Uplink physical signal(s) maybe used by the physical layer and may not carry information originatingfrom higher layers. For example, reference signal(s) may be consideredas uplink physical signal(s). Transmitted signal(s) in slot(s) may bedescribed by one or several resource grids including, for example,subcarriers and SC-FDMA or OFDMA symbols. Antenna port(s) may be definedsuch that the channel over which symbol(s) on antenna port(s) may beconveyed and/or inferred from the channel over which other symbol(s) onthe same antenna port(s) is/are conveyed. There may be one resource gridper antenna port. The antenna port(s) used for transmission of physicalchannel(s) or signal(s) may depend on the number of antenna port(s)configured for the physical channel(s) or signal(s).

Element(s) in a resource grid may be called a resource element. Aphysical resource block may be defined as N consecutive SC-FDMA symbolsin the time domain and/or M consecutive subcarriers in the frequencydomain, wherein M and N may be pre-defined integer values. Physicalresource block(s) in uplink(s) may comprise of M×N resource elements.For example, a physical resource block may correspond to one slot in thetime domain and 180 kHz in the frequency domain. Baseband signal(s)representing the physical uplink shared channel may be defined in termsof: a) scrambling, b) modulation of scrambled bits to generatecomplex-valued symbols, c) mapping of complex-valued modulation symbolsonto one or several transmission layers, d) transform precoding togenerate complex-valued symbols, e) precoding of complex-valued symbols,f) mapping of precoded complex-valued symbols to resource elements, g)generation of complex-valued time-domain SC-FDMA signal(s) for antennaport(s), and/or the like.

For codeword(s), block(s) of bits may be scrambled with UE-specificscrambling sequence(s) prior to modulation, resulting in block(s) ofscrambled bits. Complex-valued modulation symbols for codeword(s) to betransmitted may be mapped onto one, two, or more layers. For spatialmultiplexing, layer mapping(s) may be performed according to pre-definedformula(s). The number of layers may be less than or equal to the numberof antenna port(s) used for transmission of physical uplink sharedchannel(s). The example of a single codeword mapped to multiple layersmay be applicable when the number of antenna port(s) used for PUSCH is,for example, four. For layer(s), the block of complex-valued symbols maybe divided into multiple sets, each corresponding to one SC-FDMA symbol.Transform precoding may be applied. For antenna port(s) used fortransmission of the PUSCH in a subframe, block(s) of complex-valuedsymbols may be multiplied with an amplitude scaling factor in order toconform to a required transmit power, and mapped in sequence to physicalresource block(s) on antenna port(s) and assigned for transmission ofPUSCH.

According to some of the various embodiments, data may arrive to thecoding unit in the form of two transport blocks every transmission timeinterval (TTI) per UL cell. The following coding actions may beidentified for transport block(s) of an uplink carrier: a) Add CRC tothe transport block, b) Code block segmentation and code block CRCattachment, c) Channel coding of data and control information, d) Ratematching, e) Code block concatenation. f) Multiplexing of data andcontrol information, g) Channel interleaver, h) Error detection may beprovided on UL-SCH (uplink shared channel) transport block(s) through aCyclic Redundancy Check (CRC), and/or the like. Transport block(s) maybe used to calculate CRC parity bits. Code block(s) may be delivered tochannel coding block(s). Code block(s) may be individually turboencoded. Turbo coded block(s) may be delivered to rate matchingblock(s).

Physical uplink control channel(s) (PUCCH) may carry uplink controlinformation. Simultaneous transmission of PUCCH and PUSCH from the sameUE may be supported if enabled by higher layers. For a type 2 framestructure, the PUCCH may not be transmitted in the UpPTS field. PUCCHmay use one resource block in each of the two slots in a subframe.Resources allocated to UE and PUCCH configuration(s) may be transmittedvia control messages. PUCCH may comprise: a) positive and negativeacknowledgements for data packets transmitted at least one downlinkcarrier, b) channel state information for at least one downlink carrier,c) scheduling request, and/or the like.

According to some of the various aspects of embodiments, cell search maybe the procedure by which a wireless device may acquire time andfrequency synchronization with a cell and may detect the physical layerCell ID of that cell (transmitter). An example embodiment forsynchronization signal and cell search is presented below. A cell searchmay support a scalable overall transmission bandwidth corresponding to 6resource blocks and upwards. Primary and secondary synchronizationsignals may be transmitted in the downlink and may facilitate cellsearch. For example, 504 unique physical-layer cell identities may bedefined using synchronization signals. The physical-layer cellidentities may be grouped into 168 unique physical-layer cell-identitygroups, group(s) containing three unique identities. The grouping may besuch that physical-layer cell identit(ies) is part of a physical-layercell-identity group. A physical-layer cell identity may be defined by anumber in the range of 0 to 167, representing the physical-layercell-identity group, and a number in the range of 0 to 2, representingthe physical-layer identity within the physical-layer cell-identitygroup. The synchronization signal may include a primary synchronizationsignal and a secondary synchronization signal.

According to some of the various aspects of embodiments, the sequenceused for a primary synchronization signal may be generated from afrequency-domain Zadoff-Chu sequence according to a pre-defined formula.A Zadoff-Chu root sequence index may also be predefined in aspecification. The mapping of the sequence to resource elements maydepend on a frame structure. The wireless device may not assume that theprimary synchronization signal is transmitted on the same antenna portas any of the downlink reference signals. The wireless device may notassume that any transmission instance of the primary synchronizationsignal is transmitted on the same antenna port, or ports, used for anyother transmission instance of the primary synchronization signal. Thesequence may be mapped to the resource elements according to apredefined formula.

For FDD frame structure, a primary synchronization signal may be mappedto the last OFDM symbol in slots 0 and 10. For TDD frame structure, theprimary synchronization signal may be mapped to the third OFDM symbol insubframes 1 and 6. Some of the resource elements allocated to primary orsecondary synchronization signals may be reserved and not used fortransmission of the primary synchronization signal.

According to some of the various aspects of embodiments, the sequenceused for a secondary synchronization signal may be an interleavedconcatenation of two length-31 binary sequences. The concatenatedsequence may be scrambled with a scrambling sequence given by a primarysynchronization signal. The combination of two length-31 sequencesdefining the secondary synchronization signal may differ betweensubframe 0 and subframe 5 according to predefined formula(s). Themapping of the sequence to resource elements may depend on the framestructure. In a subframe for FDD frame structure and in a half-frame forTDD frame structure, the same antenna port as for the primarysynchronization signal may be used for the secondary synchronizationsignal. The sequence may be mapped to resource elements according to apredefined formula.

Example embodiments for the physical channels configuration will now bepresented. Other examples may also be possible. A physical broadcastchannel may be scrambled with a cell-specific sequence prior tomodulation, resulting in a block of scrambled bits. PBCH may bemodulated using QPSK, and/or the like. The block of complex-valuedsymbols for antenna port(s) may be transmitted during consecutive radioframes, for example, four consecutive radio frames. In some embodimentsthe PBCH data may arrive to the coding unit in the form of a onetransport block every transmission time interval (TTI) of 40 ms. Thefollowing coding actions may be identified. Add CRC to the transportblock, channel coding, and rate matching. Error detection may beprovided on PBCH transport blocks through a Cyclic Redundancy Check(CRC). The transport block may be used to calculate the CRC parity bits.The parity bits may be computed and attached to the BCH (broadcastchannel) transport block. After the attachment, the CRC bits may bescrambled according to the transmitter transmit antenna configuration.Information bits may be delivered to the channel coding block and theymay be tail biting convolutionally encoded. A tail bitingconvolutionally coded block may be delivered to the rate matching block.The coded block may be rate matched before transmission.

A master information block may be transmitted in PBCH and may includesystem information transmitted on broadcast channel(s). The masterinformation block may include downlink bandwidth, system framenumber(s), and PHICH (physical hybrid-ARQ indicator channel)configuration. Downlink bandwidth may be the transmission bandwidthconfiguration, in terms of resource blocks in a downlink, for example 6may correspond to 6 resource blocks, 15 may correspond to 15 resourceblocks and so on. System frame number(s) may define the N (for exampleN=8) most significant bits of the system frame number. The M (forexample M=2) least significant bits of the SFN may be acquiredimplicitly in the PBCH decoding. For example, timing of a 40 ms PBCH TTImay indicate 2 least significant bits (within 40 ms PBCH TTI, the firstradio frame: 00, the second radio frame: 01, the third radio frame: 10,the last radio frame: 11). One value may apply for other carriers in thesame sector of a base station (the associated functionality is common(e.g. not performed independently for each cell). PHICH configuration(s)may include PHICH duration, which may be normal (e.g. one symbolduration) or extended (e.g. 3 symbol duration).

Physical control format indicator channel(s) (PCFICH) may carryinformation about the number of OFDM symbols used for transmission ofPDCCHs (physical downlink control channel) in a subframe. The set ofOFDM symbols possible to use for PDCCH in a subframe may depend on manyparameters including, for example, downlink carrier bandwidth, in termsof downlink resource blocks. PCFICH transmitted in one subframe may bescrambled with cell-specific sequence(s) prior to modulation, resultingin a block of scrambled bits. A scrambling sequence generator(s) may beinitialized at the start of subframe(s). Block (s) of scrambled bits maybe modulated using QPSK. Block(s) of modulation symbols may be mapped toat least one layer and precoded resulting in a block of vectorsrepresenting the signal for at least one antenna port. Instances ofPCFICH control channel(s) may indicate one of several (e.g. 3) possiblevalues after being decoded. The range of possible values of instance(s)of the first control channel may depend on the first carrier bandwidth.

According to some of the various embodiments, physical downlink controlchannel(s) may carry scheduling assignments and other controlinformation. The number of resource-elements not assigned to PCFICH orPHICH may be assigned to PDCCH. PDCCH may support multiple formats.Multiple PDCCH packets may be transmitted in a subframe. PDCCH may becoded by tail biting convolutionally encoder before transmission. PDCCHbits may be scrambled with a cell-specific sequence prior to modulation,resulting in block(s) of scrambled bits. Scrambling sequencegenerator(s) may be initialized at the start of subframe(s). Block(s) ofscrambled bits may be modulated using QPSK. Block(s) of modulationsymbols may be mapped to at least one layer and precoded resulting in ablock of vectors representing the signal for at least one antenna port.PDCCH may be transmitted on the same set of antenna ports as the PBCH,wherein PBCH is a physical broadcast channel broadcasting at least onebasic system information field.

According to some of the various embodiments, scheduling controlpacket(s) may be transmitted for packet(s) or group(s) of packetstransmitted in downlink shared channel(s). Scheduling control packet(s)may include information about subcarriers used for packettransmission(s). PDCCH may also provide power control commands foruplink channels. OFDM subcarriers that are allocated for transmission ofPDCCH may occupy the bandwidth of downlink carrier(s). PDCCH channel(s)may carry a plurality of downlink control packets in subframe(s). PDCCHmay be transmitted on downlink carrier(s) starting from the first OFDMsymbol of subframe(s), and may occupy up to multiple symbol duration(s)(e.g. 3 or 4).

According to some of the various embodiments, PHICH may carry thehybrid-ARQ (automatic repeat request) ACK/NACK. Multiple PHICHs mappedto the same set of resource elements may constitute a PHICH group, wherePHICHs within the same PHICH group may be separated through differentorthogonal sequences. PHICH resource(s) may be identified by the indexpair (group, sequence), where group(s) may be the PHICH group number(s)and sequence(s) may be the orthogonal sequence index within thegroup(s). For frame structure type 1, the number of PHICH groups maydepend on parameters from higher layers (RRC). For frame structure type2, the number of PHICH groups may vary between downlink subframesaccording to a pre-defined arrangement. Block(s) of bits transmitted onone PHICH in one subframe may be modulated using BPSK or QPSK, resultingin a block(s) of complex-valued modulation symbols. Block(s) ofmodulation symbols may be symbol-wise multiplied with an orthogonalsequence and scrambled, resulting in a sequence of modulation symbols

Other arrangements for PCFICH, PHICH, PDCCH, and/or PDSCH may besupported. The configurations presented here are for example purposes.In another example, resources PCFICH, PHICH, and/or PDCCH radioresources may be transmitted in radio resources including a subset ofsubcarriers and pre-defined time duration in each or some of thesubframes. In an example, PUSCH resource(s) may start from the firstsymbol. In another example embodiment, radio resource configuration(s)for PUSCH, PUCCH, and/or PRACH (physical random access channel) may usea different configuration. For example, channels may be timemultiplexed, or time/frequency multiplexed when mapped to uplink radioresources.

According to some of the various aspects of embodiments, controlmessage(s) or control packet(s) may be scheduled for transmission in aphysical downlink shared channel (PDSCH) and/or physical uplink sharedchannel PUSCH. PDSCH and PUSCH may carry control and datamessage(s)/packet(s). Control message(s) and/or packet(s) may beprocessed before transmission. For example, the control message(s)and/or packet(s) may be fragmented or multiplexed before transmission. Acontrol message in an upper layer may be processed as a data packet inthe MAC or physical layer. For example, system information block(s) aswell as data traffic may be scheduled for transmission in PDSCH. Datapacket(s) may be encrypted packets.

According to some of the various aspects of embodiments, data packet(s)may be encrypted before transmission to secure packet(s) from unwantedreceiver(s). Desired recipient(s) may be able to decrypt the packet(s).A first plurality of data packet(s) and/or a second plurality of datapacket(s) may be encrypted using an encryption key and at least oneparameter that may change substantially rapidly over time. Theencryption mechanism may provide a transmission that may not be easilyeavesdropped by unwanted receivers. The encryption mechanism may includeadditional parameter(s) in an encryption module that changessubstantially rapidly in time to enhance the security mechanism. Examplevarying parameter(s) may comprise various types of system counter(s),such as system frame number. Substantially rapidly may for example implychanging on a per subframe, frame, or group of subframes basis.Encryption may be provided by a PDCP layer between the transmitter andreceiver, and/or may be provided by the application layer. Additionaloverhead added to packet(s) by lower layers such as RLC, MAC, and/orPhysical layer may not be encrypted before transmission. In thereceiver, the plurality of encrypted data packet(s) may be decryptedusing a first decryption key and at least one first parameter. Theplurality of data packet(s) may be decrypted using an additionalparameter that changes substantially rapidly over time.

According to some of the various aspects of embodiments, a wirelessdevice may be preconfigured with one or more carriers. When the wirelessdevice is configured with more than one carrier, the base station and/orwireless device may activate and/or deactivate the configured carriers.One of the carriers (the primary carrier) may always be activated. Othercarriers may be deactivated by default and/or may be activated by a basestation when needed. A base station may activate and deactivate carriersby sending an activation/deactivation MAC control element. Furthermore,the UE may maintain a carrier deactivation timer per configured carrierand deactivate the associated carrier upon its expiry. The same initialtimer value may apply to instance(s) of the carrier deactivation timer.The initial value of the timer may be configured by a network. Theconfigured carriers (unless the primary carrier) may be initiallydeactivated upon addition and after a handover.

According to some of the various aspects of embodiments, if a wirelessdevice receives an activation/deactivation MAC control elementactivating the carrier, the wireless device may activate the carrier,and/or may apply normal carrier operation including: sounding referencesignal transmissions on the carrier, CQI (channel quality indicator)/PMI(precoding matrix indicator)/RI (ranking indicator) reporting for thecarrier, PDCCH monitoring on the carrier, PDCCH monitoring for thecarrier, start or restart the carrier deactivation timer associated withthe carrier, and/or the like. If the device receives anactivation/deactivation MAC control element deactivating the carrier,and/or if the carrier deactivation timer associated with the activatedcarrier expires, the base station or device may deactivate the carrier,and may stop the carrier deactivation timer associated with the carrier,and/or may flush HARQ buffers associated with the carrier.

If PDCCH on a carrier scheduling the activated carrier indicates anuplink grant or a downlink assignment for the activated carrier, thedevice may restart the carrier deactivation timer associated with thecarrier. When a carrier is deactivated, the wireless device may nottransmit SRS (sounding reference signal) for the carrier, may not reportCQI/PMI/RI for the carrier, may not transmit on UL-SCH for the carrier,may not monitor the PDCCH on the carrier, and/or may not monitor thePDCCH for the carrier.

A process to assign subcarriers to data packets may be executed by a MAClayer scheduler. The decision on assigning subcarriers to a packet maybe made based on data packet size, resources required for transmissionof data packets (number of radio resource blocks), modulation and codingassigned to data packet(s), QoS required by the data packets (i.e. QoSparameters assigned to data packet bearer), the service class of asubscriber receiving the data packet, or subscriber device capability, acombination of the above, and/or the like.

According to some of the various aspects of embodiments, packets may bereferred to service data units and/or protocols data units at Layer 1,Layer 2 and/or Layer 3 of the communications network. Layer 2 in an LTEnetwork may include three sub-layers: PDCP sub-layer, RLC sub-layer, andMAC sub-layer. A layer 2 packet may be a PDCP packet, an RLC packet or aMAC layer packet. Layer 3 in an LTE network may be Internet Protocol(IP) layer, and a layer 3 packet may be an IP data packet. Packets maybe transmitted and received via an air interface physical layer. Apacket at the physical layer may be called a transport block. Many ofthe various embodiments may be implemented at one or many differentcommunication network layers. For example, some of the actions may beexecuted by the PDCP layer and some others by the MAC layer.

According to some of the various aspects of embodiments, subcarriersand/or resource blocks may comprise a plurality of physical subcarriersand/or resource blocks. In another example embodiment, subcarriers maybe a plurality of virtual and/or logical subcarriers and/or resourceblocks.

According to some of the various aspects of embodiments, a radio bearermay be a GBR (guaranteed bit rate) bearer and/or a non-GBR bearer. A GBRand/or guaranteed bit rate bearer may be employed for transfer ofreal-time packets, and/or a non-GBR bearer may be used for transfer ofnon-real-time packets. The non-GBR bearer may be assigned a plurality ofattributes including: a scheduling priority, an allocation and retentionpriority, a portable device aggregate maximum bit rate, and/or the like.These parameters may be used by the scheduler in scheduling non-GBRpackets. GBR bearers may be assigned attributes such as delay, jitter,packet loss parameters, and/or the like.

According to some of the various aspects of embodiments, subcarriers mayinclude data subcarrier symbols and pilot subcarrier symbols. Pilotsymbols may not carry user data, and may be included in the transmissionto help the receiver to perform synchronization, channel estimationand/or signal quality detection. Base stations and wireless devices(wireless receiver) may use different methods to generate and transmitpilot symbols along with information symbols.

According to some of the various aspects of embodiments, the transmitterin the disclosed embodiments of the present invention may be a wirelessdevice (also called user equipment), a base station (also calledeNodeB), a relay node transmitter, and/or the like. The receiver in thedisclosed embodiments of the present invention may be a wireless device(also called user equipment-UE), a base station (also called eNodeB), arelay node receiver, and/or the like. According to some of the variousaspects of embodiments of the present invention, layer 1 (physicallayer) may be based on OFDMA or SC-FDMA. Time may be divided intoframe(s) with fixed duration. Frame(s) may be divided into substantiallyequally sized subframes, and subframe(s) may be divided intosubstantially equally sized slot(s). A plurality of OFDM or SC-FDMAsymbol(s) may be transmitted in slot(s). OFDMA or SC-FDMA symbol(s) maybe grouped into resource block(s). A scheduler may assign resource(s) inresource block unit(s), and/or a group of resource block unit(s).Physical resource block(s) may be resources in the physical layer, andlogical resource block(s) may be resource block(s) used by the MAClayer. Similar to virtual and physical subcarriers, resource block(s)may be mapped from logical to physical resource block(s). Logicalresource block(s) may be contiguous, but corresponding physical resourceblock(s) may be non-contiguous. Some of the various embodiments of thepresent invention may be implemented at the physical or logical resourceblock level(s).

According to some of the various aspects of embodiments, layer 2transmission may include PDCP (packet data convergence protocol), RLC(radio link control), MAC (media access control) sub-layers, and/or thelike. MAC may be responsible for the multiplexing and mapping of logicalchannels to transport channels and vice versa. A MAC layer may performchannel mapping, scheduling, random access channel procedures, uplinktiming maintenance, and/or the like.

According to some of the various aspects of embodiments, the MAC layermay map logical channel(s) carrying RLC PDUs (packet data unit) totransport channel(s). For transmission, multiple SDUs (service dataunit) from logical channel(s) may be mapped to the Transport Block (TB)to be sent over transport channel(s). For reception, TBs from transportchannel(s) may be demultiplexed and assigned to corresponding logicalchannel(s). The MAC layer may perform scheduling related function(s) inboth the uplink and downlink and thus may be responsible for transportformat selection associated with transport channel(s). This may includeHARQ functionality. Since scheduling may be done at the base station,the MAC layer may be responsible for reporting scheduling relatedinformation such as UE (user equipment or wireless device) bufferoccupancy and power headroom. It may also handle prioritization fromboth an inter-UE and intra-UE logical channel perspective. MAC may alsobe responsible for random access procedure(s) for the uplink that may beperformed following either a contention and non-contention basedprocess. UE may need to maintain timing synchronization with cell(s).The MAC layer may perform procedure(s) for periodic synchronization.

According to some of the various aspects of embodiments, the MAC layermay be responsible for the mapping of multiple logical channel(s) totransport channel(s) during transmission(s), and demultiplexing andmapping of transport channel data to logical channel(s) duringreception. A MAC PDU may include of a header that describes the formatof the PDU itself, which may include control element(s), SDUs, Padding,and/or the like. The header may be composed of multiple sub-headers, onefor constituent part(s) of the MAC PDU. The MAC may also operate in atransparent mode, where no header may be pre-pended to the PDU.Activation command(s) may be inserted into packet(s) using a MAC controlelement.

According to some of the various aspects of embodiments, the MAC layerin some wireless device(s) may report buffer size(s) of either a singleLogical Channel Group (LCG) or a group of LCGs to a base station. An LCGmay be a group of logical channels identified by an LCG ID. The mappingof logical channel(s) to LCG may be set up during radio configuration.Buffer status report(s) may be used by a MAC scheduler to assign radioresources for packet transmission from wireless device(s). HARQ and ARQprocesses may be used for packet retransmission to enhance thereliability of radio transmission and reduce the overall probability ofpacket loss.

According to some of the various aspects of embodiments, an RLCsub-layer may control the applicability and functionality of errorcorrection, concatenation, segmentation, re-segmentation, duplicatedetection, in-sequence delivery, and/or the like. Other functions of RLCmay include protocol error detection and recovery, and/or SDU discard.The RLC sub-layer may receive data from upper layer radio bearer(s)(signaling and data) called service data unit(s) (SDU). The transmissionentities in the RLC layer may convert RLC SDUs to RLC PDU afterperforming functions such as segmentation, concatenation, adding RLCheader(s), and/or the like. In the other direction, receiving entitiesmay receive RLC PDUs from the MAC layer. After performing reordering,the PDUs may be assembled back into RLC SDUs and delivered to the upperlayer. RLC interaction with a MAC layer may include: a) data transferfor uplink and downlink through logical channel(s); b) MAC notifies RLCwhen a transmission opportunity becomes available, including the size oftotal number of RLC PDUs that may be transmitted in the currenttransmission opportunity, and/or c) the MAC entity at the transmittermay inform RLC at the transmitter of HARQ transmission failure.

According to some of the various aspects of embodiments, PDCP (packetdata convergence protocol) may comprise a layer 2 sub-layer on top ofRLC sub-layer. The PDCP may be responsible for a multitude of functions.First, the PDCP layer may transfer user plane and control plane data toand from upper layer(s). PDCP layer may receive SDUs from upper layer(s)and may send PDUs to the lower layer(s). In other direction, PDCP layermay receive PDUs from the lower layer(s) and may send SDUs to upperlayer(s). Second, the PDCP may be responsible for security functions. Itmay apply ciphering (encryption) for user and control plane bearers, ifconfigured. It may also perform integrity protection for control planebearer(s), if configured. Third, the PDCP may perform header compressionservice(s) to improve the efficiency of over the air transmission. Theheader compression may be based on robust header compression (ROHC).ROHC may be performed on VOIP packets. Fourth, the PDCP may beresponsible for in-order delivery of packet(s) and duplicate detectionservice(s) to upper layer(s) after handover(s). After handover, thesource base station may transfer unacknowledged packet(s)s to targetbase station when operating in RLC acknowledged mode (AM). The targetbase station may forward packet(s)s received from the source basestation to the UE (user equipment).

In this specification, “a” and “an” and similar phrases are to beinterpreted as “at least one” and “one or more.” In this specification,the term “may” is to be interpreted as “may, for example,” In otherwords, the term “may” is indicative that the phrase following the term“may” is an example of one of a multitude of suitable possibilities thatmay, or may not, be employed to one or more of the various embodiments.If A and B are sets and every element of A is also an element of B, A iscalled a subset of B. In this specification, only non-empty sets andsubsets are considered. For example, possible subsets of B={cell1,cell2} are: {cell1}, {cell2}, and {cell1, cell2}.

Many of the elements described in the disclosed embodiments may beimplemented as modules. A module is defined here as an isolatableelement that performs a defined function and has a defined interface toother elements. The modules described in this disclosure may beimplemented in hardware, software in combination with hardware,firmware, wetware (i.e hardware with a biological element) or acombination thereof, all of which are behaviorally equivalent. Forexample, modules may be implemented as a software routine written in acomputer language configured to be executed by a hardware machine (suchas C, C++, Fortran, Java, Basic, Matlab or the like) or amodeling/simulation program such as Simulink, Stateflow, GNU Octave, orLab VIEWMathScript. Additionally, it may be possible to implementmodules using physical hardware that incorporates discrete orprogrammable analog, digital and/or quantum hardware. Examples ofprogrammable hardware comprise: computers, microcontrollers,microprocessors, application-specific integrated circuits (ASICs); fieldprogrammable gate arrays (FPGAs); and complex programmable logic devices(CPLDs). Computers, microcontrollers and microprocessors are programmedusing languages such as assembly, C, C++ or the like. FPGAs, ASICs andCPLDs are often programmed using hardware description languages (HDL)such as VHSIC hardware description language (VHDL) or Verilog thatconfigure connections between internal hardware modules with lesserfunctionality on a programmable device. Finally, it needs to beemphasized that the above mentioned technologies are often used incombination to achieve the result of a functional module.

The disclosure of this patent document incorporates material which issubject to copyright protection. The copyright owner has no objection tothe facsimile reproduction by anyone of the patent document or thepatent disclosure, as it appears in the Patent and Trademark Officepatent file or records, for the limited purposes required by law, butotherwise reserves all copyright rights whatsoever.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example, and notlimitation. It will be apparent to persons skilled in the relevantart(s) that various changes in form and detail can be made thereinwithout departing from the spirit and scope. In fact, after reading theabove description, it will be apparent to one skilled in the relevantart(s) how to implement alternative embodiments. Thus, the presentembodiments should not be limited by any of the above describedexemplary embodiments. In particular, it should be noted that, forexample purposes, the above explanation has focused on the example(s)using FDD communication systems. However, one skilled in the art willrecognize that embodiments of the invention may also be implemented inTDD communication systems. The disclosed methods and systems may beimplemented in wireless or wireline systems. The features of variousembodiments presented in this invention may be combined. One or manyfeatures (method or system) of one embodiment may be implemented inother embodiments. Only a limited number of example combinations areshown to indicate to one skilled in the art the possibility of featuresthat may be combined in various embodiments to create enhancedtransmission and reception systems and methods.

In addition, it should be understood that any figures which highlightthe functionality and advantages, are presented for example purposesonly. The disclosed architecture is sufficiently flexible andconfigurable, such that it may be utilized in ways other than thatshown. For example, the actions listed in any flowchart may bere-ordered or only optionally used in some embodiments.

Further, the purpose of the Abstract of the Disclosure is to enable theU.S. Patent and Trademark Office and the public generally, andespecially the scientists, engineers and practitioners in the art whoare not familiar with patent or legal terms or phraseology, to determinequickly from a cursory inspection the nature and essence of thetechnical disclosure of the application. The Abstract of the Disclosureis not intended to be limiting as to the scope in any way.

Finally, it is the applicant's intent that only claims that include theexpress language “means for” or “step for” be interpreted under 35U.S.C. 112, paragraph 6. Claims that do not expressly include the phrase“means for” or “step for” are not to be interpreted under 35 U.S.C. 112,paragraph 6.

What is claimed is:
 1. A method comprising: providing, by a first basestation, an overlapping coverage area with each of a plurality of secondbase stations and each of a plurality of third base stations; each ofthe plurality of second base stations: allowing access to a plurality ofwireless devices; and transmitting, to a second plurality of wirelessdevices in connected mode, a second message comprising a second subframeallocation bitmap indicating a second plurality of subframes, the secondplurality of subframes comprising a second plurality of Almost BlankSubframes, base stations in the plurality of second base stationsidentifying the same set of subframes as the second plurality of AlmostBlank Subframes; and each of the plurality of third base stations:allowing access only to a restricted subset of the plurality of wirelessdevices; and transmitting to a third plurality of wireless devices inconnected mode, a third message comprising a third subframe allocationbitmap indicating a third plurality of subframes, the third plurality ofsubframes comprising a third plurality of Almost Blank Subframes, atleast two base stations in the plurality of third base stationsidentifying different sets of subframes as the third plurality of AlmostBlank Subframes.
 2. The method of claim 1, further comprising the firstbase station transmitting a message to each of the plurality of secondbase stations, the message comprising a first pattern bitmap indicatinga first Almost Blank Subframe allocation.
 3. The method of claim 2,wherein the message further comprises a second pattern bitmap indicatinga subset of a first plurality of Almost Blank Subframes indicated by thefirst pattern bitmap, the second pattern bitmap being used to configuremeasurement parameters for a subset of the second plurality of wirelessdevices.
 4. The method of claim 1, wherein the first base station is ofa different base station type than the plurality of second base stationsand the plurality of third base stations.
 5. The method of claim 1,wherein during a majority of symbols of an Almost Blank Subframe of abase station: signals are transmitted at an Almost Blank Subframe powerlevel that is substantially lower than a transmit power during anon-Almost Blank Subframe.
 6. The method of claim 1, wherein frame andsubframe transmissions of the first base station and each of theplurality of second base stations and each of the plurality of thirdbase stations are substantially synchronized.
 7. The method of claim 1,further comprising, each of the plurality of third base stationsbroadcasting a closed subscriber group indicator and a closed subscribergroup identity.
 8. The method of claim 1, wherein the at least two basestations in the plurality of third base stations provide an overlappingcoverage area in at least a region in the service area.
 9. The method ofclaim 1, further comprising transmitting, by the first base station, afirst message to a first plurality of wireless devices in connectedmode, the first message comprising a first subframe allocation bitmapindicating a first plurality of subframes, the first plurality ofsubframes comprising a first plurality of Almost Blank Subframes,wherein the first plurality of Almost Blank Subframes and the secondplurality of Almost Blank Subframes do not have a substantial overlap intime.
 10. The method of claim 1, wherein the first message furthercomprises a first Almost Blank Subframe allocation period and a firstAlmost Blank Subframe allocation offset.
 11. The method of claim 1,wherein the first base station decreases a number of Almost BlankSubframes in the first plurality of Almost Blank Subframes after anincrease in traffic load of the first base station by an amount greaterthan a value.
 12. The method of claim 1, wherein the first base stationincreases a number of Almost Blank Subframes in the first plurality ofAlmost Blank Subframes after a decrease in traffic load of the firstbase station by an amount greater than a value.
 13. A method comprising:providing, by a first base station, an overlapping coverage area witheach of a plurality of second base stations and each of a plurality ofthird base stations; each of the plurality of second base stations:allowing access to a plurality of wireless devices; and configuring asecond plurality of Almost Blank Subframes, base stations in theplurality of second base stations configuring the same set of subframesas the second plurality of Almost Blank Subframes; and each of theplurality of third base stations: allowing access only to a restrictedsubset of the plurality of wireless devices; and configuring a thirdplurality of Almost Blank Subframes, at least two base stations in theplurality of third base stations not configuring the same set ofsubframes as the third plurality of Almost Blank Subframes; and whereinduring a majority of symbols of an Almost Blank Subframe of a basestation: signals are transmitted at an Almost Blank Subframe power levelthat is substantially lower than a transmit power during a non-AlmostBlank Subframe.
 14. The method of claim 13, wherein each base station ina plurality of base stations broadcasts the same system frame number inframes that are transmitted substantially at the same time.
 15. Themethod of claim 13, wherein each of the restricted subset of theplurality of wireless devices is configured with a closed subscribergroup white-list comprising the closed subscriber group identity of abase station in the plurality of third base stations.
 16. The method ofclaim 13, wherein the at least two base stations in the plurality ofthird base stations broadcast different closed subscriber groupidentities.
 17. The method of claim 13, wherein in the Almost BlankSubframe, a common reference signal is transmitted only in a controlregion.
 18. The method of claim 13, further comprising, each of theplurality of third base stations broadcasting a closed subscriber groupindicator and a closed subscriber group identity.
 19. The method ofclaim 13, wherein the first base station is of a different base stationtype than the plurality of second base stations and the plurality ofthird base stations.
 20. The method of claim 13, wherein frame andsubframe transmissions of the first base station and each of theplurality of second base stations and each of the plurality of thirdbase stations are substantially synchronized.